[Static Web Asssets] Change the Vary header that we add in ApplyCompressionNegotiation.cs to be Accept-Encoding instead of Content-Encoding. Make sure to run and update the ApplyCompressionNegotatiationTests.cs to reflect the change.

You will have to update the test baselines using src/RazorSdk/update-test-baselines.sh and check-in the changes. Make sure that they look correct to you by using git diff to see the changes to the .json files.

The change must include the fix in DefineStaticWebAssetEndpoints and the updated baselines. At the end, include a comment with at least one of the updated endpoints in one of the baseline files.