Bump importlib-metadata from 3.4.0 to 3.7.3

Bumps [importlib-metadata](https://github.com/python/importlib_metadata) from 3.4.0 to 3.7.3.
- [Release notes](https://github.com/python/importlib_metadata/releases)
- [Changelog](https://github.com/python/importlib_metadata/blob/main/CHANGES.rst)
- [Commits](python/importlib_metadata@v3.4.0...v3.7.3)

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

requirements/test.txt

@@ -28,7 +28,7 @@ attrs==20.3.0
 coverage==5.4
 docopt==0.6.2
 imagesize==1.2.0
-importlib-metadata==3.4.0
+importlib-metadata==3.7.3
 inflection==0.5.1
 mccabe==0.6.1
 more-itertools==8.7.0