Fix /samples redirect when no subpath (#6342)

Fixes #6340

Author: parlough

firebase.json

@@ -359,7 +359,7 @@
       { "source": "/resources/language/spec/versions", "destination": "/resources/language/spec", "type": 301 },
       { "source": "/resources/language/spec/versions/DartLangSpecDraft.pdf", "destination": "https://spec.dart.dev/DartLangSpecDraft.pdf", "type": 301 },
       { "source": "/resources/language/spec/versions/DartLangSpec-v2.2.pdf", "destination": "https://github.com/dart-lang/site-www/blob/a7f170389e210adc2aef810cc9a6fdbfa78059a5/src/guides/language/specifications/DartLangSpec-v2.2.pdf", "type": 301 },
-      { "source": "/samples/{,/**}", "destination": "/language", "type": 301 },
+      { "source": "/samples{,/**}", "destination": "/language", "type": 301 },
       { "source": "/sdk-changelog-2.4.0", "destination": "https://github.com/dart-lang/sdk/blob/main/CHANGELOG.md#240---2019-06-27", "type": 301 },
       { "source": "/server/app-engine{,/**}", "destination": "/server/google-cloud", "type": 301 },
       { "source": "/server/c-interop", "destination": "/interop/c-interop", "type": 301 },