Switch Protractor back to ^5.4.2

Protractor 6 is not yet compatible with
Angular CLI:
angular/protractor#5209

Author: gspitz01

package-lock.json

@@ -46,7 +46,7 @@
     "karma-coverage-istanbul-reporter": "~2.0.0",
     "karma-jasmine": "~1.1.1",
     "karma-jasmine-html-reporter": "^0.2.2",
-    "protractor": "^6.0.0",
+    "protractor": "^5.4.2",
     "ts-node": "~5.0.1",
     "tslint": "~5.9.1",
     "typescript": "~3.4.5"