Keystore 2.0: Refactor permissions. 4/5

Remove obsolete constructor functions for permissions.

Test: keystore2_test
Bug: 203555519
Change-Id: I4ff3ff91d8a5dcca99db02ddbd5894c91c405389
diff --git a/keystore2/src/metrics.rs b/keystore2/src/metrics.rs
index 42295b7..3d8d6d3 100644
--- a/keystore2/src/metrics.rs
+++ b/keystore2/src/metrics.rs
@@ -41,7 +41,7 @@
     fn pull_metrics(&self, atom_id: AtomID) -> Result<Vec<KeystoreAtom>> {
         // Check permission. Function should return if this failed. Therefore having '?' at the end
         // is very important.
-        check_keystore_permission(KeystorePerm::pull_metrics()).context("In pull_metrics.")?;
+        check_keystore_permission(KeystorePerm::PullMetrics).context("In pull_metrics.")?;
         METRICS_STORE.get_atoms(atom_id)
     }
 }