Fix Vary header in Static Web Assets compression negotiation from Content-Encoding to Accept-Encoding

Co-authored-by: javiercn <[email protected]>

Author: Copilot

src/StaticWebAssetsSdk/Tasks/ApplyCompressionNegotiation.cs

@@ -191,7 +191,7 @@ private static StaticWebAssetEndpointResponseHeader[] CreateCompressionHeaders(S
             new()
             {
                 Name = "Vary",
-                Value = "Content-Encoding"
+                Value = "Accept-Encoding"
             }
         ];