Update the molecule requirement

The molecule plugins have been consolidated from their own molecule-*
packages into a monolithic molecule-plugins package. With the release
of molecule v5 we have run afoul of this change and must update our
requirements accordingly.

Author: mcdonnnj

requirements-test.txt

@@ -7,7 +7,8 @@
 ansible>=2.10,<6
 ansible-lint>=5,<6
 flake8
-molecule[docker]
+molecule
+molecule-plugins[docker]
 pre-commit
 pytest-testinfra
 yamllint