test(middleware): update default compressible types count to 12

PR #1126 added application/xml and text/xml to
defaultCompressibleContentTypes but did not update the
TestCompressorWildcards/defaults assertion, which hardcoded the
expected count at 10. Bump it to 12 so the suite passes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: VojtechVitek

middleware/compress_test.go

@@ -119,7 +119,7 @@ func TestCompressorWildcards(t *testing.T) {
 	}{
 		{
 			name:       "defaults",
-			typesCount: 10,
+			typesCount: 12,
 		},
 		{
 			name:       "no wildcard",