Fix broken links in docs

[rly]

Motivation

The conda-forge page changed and the #about anchor is gone. We should probably avoid linking to anchors since they change more frequently than base URLs.

Sphinx link-check cannot detect/resolve https://github.com/NeurodataWithoutBorders/pynwb#readme . It seems like GitHub dynamically generates this anchor. This code sphinx-doc/sphinx@master/sphinx/builders/linkcheck.py#L616 would normally detect it, but it looks like something changed with the GitHub layout a few days ago - there are now tabs on the main repo page for readme, code of conduct, and license.

This is minor enough not to need a changelog entry.

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (883b1b1) 91.99% compared to head (bd4989f) 91.99%.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #1816   +/-   ##
=======================================
  Coverage   91.99%   91.99%           
=======================================
  Files          27       27           
  Lines        2623     2623           
  Branches      685      685           
=======================================
  Hits         2413     2413           
  Misses        138      138           
  Partials       72       72           

Flag	Coverage Δ
integration	71.10% <ø> (ø)
unit	83.68% <ø> (ø)

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