[release/6.0] Reduce helix-matrix timeout to 5 hours (#54779)

* Reduce helix-matrix timeout to 3 hours

* Update helix-matrix.yml

---------

Co-authored-by: William Godbe <wigodbe@microsoft.com>

Author: github-actions[bot]

.azure/pipelines/helix-matrix.yml

@@ -28,7 +28,7 @@ jobs:
     jobName: Helix_matrix_x64
     jobDisplayName: 'Tests: Helix full matrix x64'
     agentOs: Windows
-    timeoutInMinutes: 480
+    timeoutInMinutes: 300
     steps:
     # Build the shared framework
     - script: ./eng/build.cmd -ci -nobl -all -pack -arch x64