[release/8.0.1xx] Update dependencies from dotnet/source-build-externals (#20906)

Co-authored-by: dotnet-maestro[bot] <dotnet-maestro[bot]@users.noreply.github.com>
Co-authored-by: Matt Thalman <mthalman@microsoft.com>

Author: dotnet-maestro[bot]

eng/Version.Details.xml

@@ -198,9 +198,9 @@
       <Sha>5255d40e228ea1d4b624781b5b97ec16484a3b4b</Sha>
       <SourceBuild RepoName="deployment-tools" ManagedOnly="true" />
     </Dependency>
-    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-externals" Version="8.0.0-alpha.1.26319.6">
-      <Uri>https://dev.azure.com/dnceng/internal/_git/dotnet-source-build-externals</Uri>
-      <Sha>513485b2bbf1bd0f77d69f388221fd0905b5dc65</Sha>
+    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-externals" Version="8.0.0-alpha.1.26364.1">
+      <Uri>https://github.com/dotnet/source-build-externals</Uri>
+      <Sha>f6ae6a604f59a1f59d0fbf7fec68367404ed53d1</Sha>
       <SourceBuild RepoName="source-build-externals" ManagedOnly="true" />
     </Dependency>
     <Dependency Name="Microsoft.SourceBuild.Intermediate.symreader" Version="2.1.0-beta.23253.1">