Remove unused isRunningAgainstEmulator() (#2648)

Author: schmidt-sebastian

packages/firestore/test/integration/util/helpers.ts

@@ -82,10 +82,6 @@ export function isPersistenceAvailable(): boolean {
   );
 }
 
-export function isRunningAgainstEmulator(): boolean {
-  return USE_EMULATOR;
-}
-
 /**
  * A wrapper around Mocha's describe method that allows for it to be run with
  * persistence both disabled and enabled (if the browser is supported).