zulip_bots: Remove include_package_data=True argument from setup().

According to the `setuptools` docs, once `include_package_data=True`
is passed to `setup()`, it will only include package data specified
in `MANIFEST.in`, and will ignore the `package_data` argument passed
to `setup()`. Thus, the `py.typed` file was not included in our
latest PyPI release 0.8.1.

A quick way to fix this is to remove the `include_package_data=True`
argument and to let our explicit `package_data` argument values
govern what data is included in the release.

See https://github.com/pypa/setuptools/issues/1461 for background.

zulip_bots/setup.py

@@ -55,7 +55,6 @@ package_info = dict(
             "zulip-terminal=zulip_bots.terminal:main",
         ],
     },
-    include_package_data=True,
 )  # type: Dict[str, Any]
 
 setuptools_info = dict(