python interface: increase traversal limit

Sometimes, when iterating through the repository, it would throw:
KjException: capnp/arena.c++:130: failed: Exceeded message traversal limit.  See capnp::ReaderOptions.

The limit is likely meant to be a message-size-bomb-attack prevention. No need for that here.

python/bb_binary/repository.py

@@ -35,7 +35,7 @@ def _mkdir_p(path):
 def load_frame_container(fname):
     """Loads :obj:`.FrameContainer` from this filename."""
     with open(fname, 'rb') as f:
-        return FrameContainer.read(f)
+        return FrameContainer.read(f, traversal_limit_in_words=2**63)
 
 
 class Repository(object):