devel/py-tox: Fix RUN_DEPENDS after cd1f80795973dc010a788cdbf90cece3473e36f4

• Fix RUN_DEPENDS version requirement of RUN_DEPENDS [1]
• While I'm here:
  • Fix (part of) version requirement of TEST_DEPENDS [2][3][4]
  • Remove superfluous ',' in *_DEPENDS
  • Use PYTHON_REL instead of PYTHON_VER

Note that TEST_DEPENDS needs to be updated to match upstream and current ports tree.

Reference: https://github.com/tox-dev/tox/blob/3.25.0/setup.cfg#L46 [1]

		https://github.com/tox-dev/tox/blob/3.25.0/setup.cfg#L71 [2]
		https://github.com/tox-dev/tox/blob/3.25.0/setup.cfg#L72 [3]
		https://github.com/tox-dev/tox/blob/3.25.0/setup.cfg#L74 [4]