Fixed copy-paste error in docs

[jmwright]

Also fixed the DOI badge to close #743

[codecov]

Codecov Report

Merging #748 (052c53a) into master (c6c1956) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #748   +/-   ##
=======================================
  Coverage   94.64%   94.64%           
=======================================
  Files          32       32           
  Lines        7249     7249           
  Branches      789      789           
=======================================
  Hits         6861     6861           
  Misses        255      255           
  Partials      133      133           

Impacted Files	Coverage Δ
cadquery/cq.py	91.32% <ø> (ø)

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[jmwright]

This is a pretty straight-forward fix, so I'm going to go ahead and merge.

[fedorkotov]

Your commit does not change anything in README and after merging I still don't see DOI badge

(Firefox 88.0 64-bit, Windows 8.1)