ci: stride-docs-test-build.yml - Use official docfx main branch

- Update workflow to check out dotnet/docfx main branch
- Replace usage of filzrev/docfx feat-add-net10-support fork
- Ensures workflow uses upstream, stable DocFX version

Author: VaclavElias

.github/workflows/stride-docs-test-build.yml

@@ -23,7 +23,7 @@ jobs:
 
     # Checkout the Stride Docs repository from the branch that triggered the workflow
     - name: Checkout Stride Docs
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         path: ${{ env.DOCS_PATH }}
         lfs: true
@@ -45,7 +45,7 @@ jobs:
 
     # Checkout the Stride repository from the default branch
     - name: Checkout Stride (note the LFS)
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         repository: stride3d/stride
         token: ${{ secrets.GITHUB_TOKEN }}
@@ -54,11 +54,12 @@ jobs:
         ref: master
 
     # Temporary solution till the new docfx is available
-    - name: Checkout DocFX PR Branch
-      uses: actions/checkout@v5
+    - name: Checkout DocFX
+      uses: actions/checkout@v6
       with:
-        repository: filzrev/docfx
-        ref: feat-add-net10-support
+        repository: dotnet/docfx
+        # Tested commit
+        ref: 917cda8
         path: docfx-build
 
     - name: Restore npm dependencies