Update error string check in compat test.

Author: DellaBitta

packages/database-compat/test/database.test.ts

@@ -301,7 +301,7 @@ describe('Database Tests', () => {
 
     expect(() => {
       db.useEmulator('localhost', 1234);
-    }).to.throw(/Cannot call useEmulator/);
+    }).to.throw(/connectDatabaseEmulator() cannot initialize/);
   });
 
   it('refFromURL returns an emulated ref with useEmulator', () => {

packages/database/src/api/Database.ts

@@ -364,7 +364,7 @@ export function connectDatabaseEmulator(
       return;
     }
     fatal(
-      'connectDatabaseEmulator() cannot alter the emulator configuration after the database instance has started.'
+      'connectDatabaseEmulator() cannot initialize or alter the emulator configuration after the database instance has started.'
     );
   }