Replace raw JSON with makeSymbolGraph() helper

Use makeSymbolGraph() helper instead of raw JSON strings for cleaner
and more maintainable test code, as suggested in PR review.

Author: agisilaos

Tests/SwiftDocCTests/Infrastructure/DocumentationContext/DocumentationContext+RootPageTests.swift

@@ -267,108 +267,10 @@ class DocumentationContext_RootPageTests: XCTestCase {
         let (_, context) = try await loadBundle(catalog:
             Folder(name: "multiple-modules.docc", content: [
                 // First module symbol graph
-                TextFile(name: "ModuleA.symbols.json", utf8Content: """
-                {
-                  "metadata": {
-                    "formatVersion": {
-                      "major": 1,
-                      "minor": 0,
-                      "patch": 0
-                    },
-                    "generator": "unit-test"
-                  },
-                  "module": {
-                    "name": "ModuleA",
-                    "platform": {
-                      "architecture": "x86_64",
-                      "vendor": "apple",
-                      "operatingSystem": {
-                        "name": "macosx",
-                        "minimumVersion": {
-                          "major": 10,
-                          "minor": 15
-                        }
-                      },
-                      "environment": null
-                    }
-                  },
-                  "symbols": [
-                    {
-                      "identifier": {
-                        "precise": "ModuleA",
-                        "interfaceLanguage": "swift"
-                      },
-                      "names": {
-                        "title": "ModuleA",
-                        "navigator": null,
-                        "subHeading": null,
-                        "prose": null
-                      },
-                      "pathComponents": ["ModuleA"],
-                      "docComment": null,
-                      "accessLevel": "public",
-                      "kind": {
-                        "identifier": "module",
-                        "displayName": "Module"
-                      },
-                      "mixins": {}
-                    }
-                  ],
-                  "relationships": []
-                }
-                """),
+                JSONFile(name: "ModuleA.symbols.json", content: makeSymbolGraph(moduleName: "ModuleA")),
 
                 // Second module symbol graph
-                TextFile(name: "ModuleB.symbols.json", utf8Content: """
-                {
-                  "metadata": {
-                    "formatVersion": {
-                      "major": 1,
-                      "minor": 0,
-                      "patch": 0
-                    },
-                    "generator": "unit-test"
-                  },
-                  "module": {
-                    "name": "ModuleB",
-                    "platform": {
-                      "architecture": "x86_64",
-                      "vendor": "apple",
-                      "operatingSystem": {
-                        "name": "macosx",
-                        "minimumVersion": {
-                          "major": 10,
-                          "minor": 15
-                        }
-                      },
-                      "environment": null
-                    }
-                  },
-                  "symbols": [
-                    {
-                      "identifier": {
-                        "precise": "ModuleB",
-                        "interfaceLanguage": "swift"
-                      },
-                      "names": {
-                        "title": "ModuleB",
-                        "navigator": null,
-                        "subHeading": null,
-                        "prose": null
-                      },
-                      "pathComponents": ["ModuleB"],
-                      "docComment": null,
-                      "accessLevel": "public",
-                      "kind": {
-                        "identifier": "module",
-                        "displayName": "Module"
-                      },
-                      "mixins": {}
-                    }
-                  ],
-                  "relationships": []
-                }
-                """),
+                JSONFile(name: "ModuleB.symbols.json", content: makeSymbolGraph(moduleName: "ModuleB")),
 
                 InfoPlist(displayName: "TestBundle", identifier: "com.test.example"),
             ])