Update comment

eng/Version.Details.xml

@@ -6,8 +6,9 @@
       <Sha>525b6c35cc5c5c9b80b47044be2e4e77858d505a</Sha>
       <SourceBuild RepoName="source-build-reference-packages" ManagedOnly="true" />
     </Dependency>
-    <!-- Necessary for source-build. This allows the package to be retrieved from previously-source-built artifacts
-      and flow in as dependencies of the packages produced by msbuild. -->
+    <!-- Necessary for source-build due to being a transitive dependency of System.Reflection.MetadataLoadContext.
+      This allows the package to be retrieved from previously-source-built artifacts and flow in as dependencies
+      of the packages produced by msbuild. -->
     <Dependency Name="System.Collections.Immutable" Version="7.0.0">
       <Uri>https://github.com/dotnet/runtime</Uri>
       <Sha>d099f075e45d2aa6007a22b71b45a08758559f80</Sha>