Do not mark interpolation tokens as strings in C# (#232772)

Co-authored-by: Alex Ross <alros@microsoft.com>

extensions/csharp/package.json

@@ -37,7 +37,10 @@
       {
         "language": "csharp",
         "scopeName": "source.cs",
-        "path": "./syntaxes/csharp.tmLanguage.json"
+        "path": "./syntaxes/csharp.tmLanguage.json",
+        "tokenTypes": {
+          "meta.interpolation": "other"
+        }
       }
     ],
     "snippets": [