Bump importlib-metadata to 4.12.0

Reference: https://pypi.org/project/importlib-metadata/#history
Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

tests/test_resolution.py

@@ -82,7 +82,7 @@ def test_get_resolved_dependencies_with_flask_and_python_36():
     assert as_list == [
         "pkg:pypi/click@8.1.3",
         "pkg:pypi/flask@2.1.2",
-        "pkg:pypi/importlib-metadata@4.11.4",
+        "pkg:pypi/importlib-metadata@4.12.0",
         "pkg:pypi/itsdangerous@2.1.2",
         "pkg:pypi/jinja2@3.1.2",
         "pkg:pypi/markupsafe@2.0.1",
@@ -107,7 +107,7 @@ def test_get_resolved_dependencies_with_tilde_requirement_using_json_api():
     assert as_list == [
         "pkg:pypi/click@8.1.3",
         "pkg:pypi/flask@2.1.2",
-        "pkg:pypi/importlib-metadata@4.11.4",
+        "pkg:pypi/importlib-metadata@4.12.0",
         "pkg:pypi/itsdangerous@2.1.2",
         "pkg:pypi/jinja2@3.1.2",
         "pkg:pypi/markupsafe@2.1.1",