Fix storage cell constructor args

When we changed the constructors for the V2 cells with the
introduction of V5 format, these call sites didn't get updated.  This
doesn't seem to be a user-facing bug, and did not affect any releases.

This was caught by a compiler upgrade.

Issue #2528

Change-Id: I77228d17631ef44a6b85a81b88054790461617bc

lib/offline/indexeddb/storage_mechanism.js

@@ -216,8 +216,7 @@ shaka.offline.indexeddb.StorageMechanism = class {
       return new shaka.offline.indexeddb.V2StorageCell(
           db,
           segmentStore,
-          manifestStore,
-          true);  // Are keys locked? Yes, this means no new additions.
+          manifestStore);
     }
     return null;
   }
@@ -240,8 +239,7 @@ shaka.offline.indexeddb.StorageMechanism = class {
       return new shaka.offline.indexeddb.V2StorageCell(
           db,
           segmentStore,
-          manifestStore,
-          false); // Are keys locked? No, this means we can add new entries.
+          manifestStore);
     }
     return null;
   }