Fix checkout_code: Remove Metro cache check (facebook#21998)

Summary:
This was a specific check that was prone to break at some point. That time has come. Removing it as it is not providing any useful signal.
Pull Request resolved: facebook#21998

Differential Revision: D12823839

Pulled By: hramos

fbshipit-source-id: e870670d7803af78c4559052613ea364ce1478df

Author: hramos

.circleci/config.yml

@@ -197,7 +197,6 @@ aliases:
     name: Sanity checks
     command: |
       ./scripts/circleci/check_license.sh
-      ./scripts/circleci/check_cache.sh
       ./scripts/circleci/validate_yarn_lockfile.sh
     when: always