Update helix-matrix.yml (#30229)

Author: captainsafia

.azure/pipelines/helix-matrix.yml

@@ -38,7 +38,7 @@ jobs:
     - script: ./eng/build.cmd -ci -nobl -noBuildRepoTasks -restore -noBuild -noBuildNative -projects src/Grpc/**/*.csproj
               /p:CrossgenOutput=false /p:ASPNETCORE_TEST_LOG_DIR=artifacts/log
       displayName: Restore interop projects
-    - script: .\build.cmd -ci -nobl -noBuildRepoTasks -NoRestore -test -all -noBuildNative -projects eng\helix\helix.proj
+    - script: .\eng\build.cmd -ci -nobl -noBuildRepoTasks -NoRestore -test -all -noBuildNative -projects eng\helix\helix.proj
               /p:IsHelixDaily=true /p:IsRequiredCheck=true /p:IsHelixJob=true /p:BuildInteropProjects=true
               /p:RunTemplateTests=true /p:CrossgenOutput=false /p:ASPNETCORE_TEST_LOG_DIR=artifacts/log
       displayName: Run build.cmd helix target