Revert "Enable preferRest option by default for Firestore functions" (#6520)

* revert enabling preferrest by default

Author: blidd-google

CHANGELOG.md

@@ -1,3 +1,4 @@
+- Revert enabling preferRest by default to avoid performance degradations for some users (#6520).
 - Fix blocking functions in the emulator when using multiple codebases (#6504).
 - Add force flag call-out for bypassing prompts (#6506).
 - Fixed an issue where the functions emulator did not respect the `--log-verbosity` flag (#2859).

src/functions/env.ts

@@ -410,6 +410,5 @@ export function loadFirebaseEnvs(
   return {
     FIREBASE_CONFIG: JSON.stringify(firebaseConfig),
     GCLOUD_PROJECT: projectId,
-    FIRESTORE_PREFER_REST: "true",
   };
 }