language/python: link manpages by default

[cho-m]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

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Seems okay to make default. Been a couple years since I added this and haven't seen any issues with ones we've manually enabled. May as well expose the man pages if they are already installed and manually disable any that cause issues.

[MikeMcQuaid]

Good idea.