repo: Drop unused cache variables leftover from pack files

These are leftovers from the packfile code and should have been
deleted in commit: 2a0601efc7

I noticed this now since I wanted to add a new type of caching.

Closes: #795
Approved by: jlebon

src/libostree/ostree-repo-private.h

@@ -92,8 +92,6 @@ struct OstreeRepo {
   OstreeRepoTransactionStats txn_stats;
 
   GMutex cache_lock;
-  GPtrArray *cached_meta_indexes;
-  GPtrArray *cached_content_indexes;
 
   gboolean inited;
   gboolean writable;

src/libostree/ostree-repo.c

@@ -536,8 +536,6 @@ ostree_repo_finalize (GObject *object)
   if (self->config)
     g_key_file_free (self->config);
   g_clear_pointer (&self->txn_refs, g_hash_table_destroy);
-  g_clear_pointer (&self->cached_meta_indexes, (GDestroyNotify) g_ptr_array_unref);
-  g_clear_pointer (&self->cached_content_indexes, (GDestroyNotify) g_ptr_array_unref);
   g_clear_error (&self->writable_error);
   g_clear_pointer (&self->object_sizes, (GDestroyNotify) g_hash_table_unref);
   g_mutex_clear (&self->cache_lock);