test(docs-infra): unnest unnecessarily nested test suite (#42452)

Previously, the `destinations` test suite in
`testFirebaseRedirection.spec.ts` was nested under the
`with legacy URLs` test suite. However, the two suites are unrelated and
there is no reason to have them nested.

This commit moves the `destinations` test suite to be beside (instead of
inside) the `with legacy URLs` one.

PR Close #42452

aio/tests/deployment/unit/testFirebaseRedirection.spec.ts

@@ -24,6 +24,7 @@ describe('firebase.json redirect config', () => {
         }
       });
     });
+  });
 
   describe('destinations', () => {
     loadRedirects().forEach(redirect => {
@@ -32,5 +33,4 @@ describe('firebase.json redirect config', () => {
       });
     });
   });
-  });
 });