Bump mgrs from 1.3.7 to 1.3.8

Bumps [mgrs](https://github.com/hobu/mgrs) from 1.3.7 to 1.3.8.
- [Release notes](https://github.com/hobu/mgrs/releases)
- [Commits](https://github.com/hobu/mgrs/compare/1.3.7...1.3.8)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

setup.py

@@ -46,7 +46,7 @@ setup(
         'shapely==1.7.1',
         'ogn-client==0.9.7',
         'psycopg2-binary==2.8.5',
-        'mgrs==1.3.7',
+        'mgrs==1.3.8',
         'xmlunittest==0.5.0',
         'flower==0.9.5',
         'tqdm==4.48.0',