compatibility: Require version 16.2.96+ for our Android app.

This release is from 2018-08-22, a little over 100 days ago.

It was the first release with the important fix so that when the
server advises it to stop displaying a notification because the user
has read the message (as the SEND_REMOVE_PUSH_NOTIFICATIONS server
setting enables), the app doesn't instead replace the notification
with a broken one reading "null".  We have that setting running now
on chat.zulip.org, and intend to roll it out more broadly soon.

The `# take 0` thing is a slightly absurd workaround for the fact
that our funky out-of-line way of marking lines to ignore doesn't
work right if there are multiple such lines in a given file that
are equal modulo leading and trailing whitespace.

tools/linter_lib/custom_check.py

@@ -501,6 +501,7 @@ def build_custom_checkers(by_lang):
          'exclude': set(['zerver/tests']),
          'exclude_line': set([
              # We don't want this string tagged for translation.
+             ('zerver/views/compatibility.py', 'return json_error("Client is too old")  # take 0'),
              ('zerver/views/compatibility.py', 'return json_error("Client is too old")'),
          ]),
          'description': 'Argument to json_error should a literal string enclosed by _()'},