Remove unnecessary mutex lock

Unsure if this is _should_ be removed, but we will remove for the time
being. The sqlite docs make a call out that this return value is
meaningless if another thread is making changes on the DB.

Author: warmwaffles

c_src/sqlite3_nif.c

@@ -363,9 +363,7 @@ exqlite_changes(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
         return make_error_tuple(env, am_connection_closed);
     }
 
-    enif_mutex_lock(conn->mutex);
     int changes = sqlite3_changes(conn->db);
-    enif_mutex_unlock(conn->mutex);
     return make_ok_tuple(env, enif_make_int(env, changes));
 }