Update PR template doc links

[rcomer]

PR summary

Looks like documentation guidance has been updated more recently than the PR template. The links are currently all getting redirected to the top of the doc guidance page.

PR checklist

• "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

[jklymak]

I'd just have one link to the dev guide. This wall of text is probably not read by anyone.

[rcomer]

I think the checklist is useful: I certainly paid attention to it when I opened my first PR here, and I still sometimes need the reminder to add a versionadded directive. I’m not sure I ever really noticed the long comment below the checklist though.