[3.7] Fix CI badge in docs (#5252)

[aio-libs-github-bot]

Backports the following commits to 3.7:

• Fix CI badge in docs (#5252)

[codecov]

Codecov Report

Merging #5254 (29fbb5d) into 3.7 (29d167e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              3.7    #5254   +/-   ##
=======================================
  Coverage   97.55%   97.55%           
=======================================
  Files          44       44           
  Lines        8818     8818           
  Branches     1419     1419           
=======================================
  Hits         8602     8602           
  Misses        101      101           
  Partials      115      115           

Flag	Coverage Δ
unit	97.39% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 29d167e...29fbb5d. Read the comment docs.