cleanup: Delete leading newlines.

Previous cleanups (mostly the removals of Python __future__ imports)
were done in a way that introduced leading newlines.  Delete leading
newlines from all files, except static/assets/zulip-emoji/NOTICE,
which is a verbatim copy of the Apache 2.0 license.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

scripts/lib/node_cache.py

@@ -1,4 +1,3 @@
-
 import os
 import hashlib
 import json