Fix hyperlinks in docs and docstrings with updated address

[gsheni]

Pull Request Description

• The ecosystem is incorrect and doesn't currently work. This PR fixes that.
• There are additional links which have the same problem, and this PR addresses that.

[codecov]

Codecov Report

Merging #910 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #910   +/-   ##
=======================================
  Coverage   98.17%   98.17%           
=======================================
  Files         119      119           
  Lines       10850    10850           
=======================================
  Hits        10652    10652           
  Misses        198      198           

Impacted Files	Coverage Δ
featuretools/computational_backends/utils.py	94.11% <ø> (ø)
featuretools/entityset/entityset.py	96.48% <ø> (ø)

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[rwedge]

Can you do a sweep of the repo for any other links that references specific pages on docs.featuretools.com and are missing the /en/stable/ part of the path?

[gsheni]

Can you do a sweep of the repo for any other links that references specific pages on docs.featuretools.com and are missing the /en/stable/ part of the path?

There was 2 more in the docstrings that I fixed.

[rwedge]

I think there's another link in docs/source/templates/layout.html that needs to be fixed

[gsheni]

I think there's another link in docs/source/templates/layout.html that needs to be fixed

Fixed.

I thought changing the link would not work since it was a static image. So I skipped it on my review. But the new link worked.

[rwedge]

Looks good