setup.py: Don't install/ship .po files

- These files are not necessary for the running of the program. Only .mo files
are referenced by gettext library at runtime.

- This reduces the size of the .deb binary.

Tests performed:

- Build Debian packages. Upgrade on a stable setup. Switch language to Spanish
and notice UI strings in Spanish.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

setup.py

@@ -305,7 +305,7 @@ setuptools.setup(
         'requests',
     ],
     package_data={
-        '': ['templates/*', 'static/*', 'locale/*/LC_MESSAGES/*.[pm]o']
+        '': ['templates/*', 'static/*', 'locale/*/LC_MESSAGES/*.mo']
     },
     exclude_package_data={'': ['*/data/*']},
     data_files=_gather_data_files() +