[release/9.0.1xx] Do not synchronize docx from the AAD submodule

https://dev.azure.com/dnceng/internal/_build/results?buildId=2996566&view=logs&j=f94b1352-8074-534d-f024-dae8a910f9a5&t=2443bf50-9ea5-59bd-ea89-63ee8561cbb0

Author: premun

src/VirtualMonoRepo/source-mappings.json

@@ -134,6 +134,7 @@
             "name": "source-build-externals",
             "defaultRemote": "https://github.com/dotnet/source-build-externals",
             "exclude": [
+                "src/azure-activedirectory-identitymodel-extensions-for-dotnet/docs/*.docx",
                 "src/application-insights/**/*.exe",
                 "src/application-insights/**/*.dll",
                 "src/application-insights/**/*.zip",