docs: clean unused link in readme

[chenxsan]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

It's a description as I see, so there's no need to add a link? And it's causing the CI failure of webpack.js.org repository https://travis-ci.org/github/webpack/webpack.js.org/jobs/734298251#L860

Breaking Changes

Additional Info

[codecov]

Codecov Report

Merging #604 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #604   +/-   ##
=======================================
  Coverage   88.51%   88.51%           
=======================================
  Files          20       20           
  Lines        1202     1202           
  Branches      310      309    -1     
=======================================
  Hits         1064     1064           
  Misses        132      132           
  Partials        6        6           

---

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 787b6d2...2435b06. Read the comment docs.

[alexander-akait]

Thanks