Fix: Memory leak when inserting keyframes with NLA offset

Introduced with #118957

When calling `BKE_animsys_get_nla_keyframing_context`
the function allocates memory, which needs to be freed later.
This was missed.

Pull Request: https://projects.blender.org/blender/blender/pulls/119208

source/blender/animrig/intern/keyframing.cc

@@ -1067,6 +1067,7 @@ void insert_key_rna(PointerRNA *rna_pointer,
                                           key_type,
                                           successful_remaps);
   }
+  BKE_animsys_free_nla_keyframing_context_cache(&nla_cache);
 
   if (insert_key_count == 0) {
     BKE_reportf(reports, RPT_ERROR, "Failed to insert any keys");