DOC: Change full commit changelog link text

[scottclowe]

Make "Full commit changelog" be the anchor text, and remove "on github".

[codecov]

Codecov Report

Merging #115 into master will increase coverage by 1.20%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #115      +/-   ##
==========================================
+ Coverage   81.09%   82.30%   +1.20%     
==========================================
  Files           9        9              
  Lines         693      695       +2     
  Branches      132      132              
==========================================
+ Hits          562      572      +10     
+ Misses         90       84       -6     
+ Partials       41       39       -2     

Impacted Files	Coverage Δ
fissa/core.py	94.51% <0.00%> (+3.45%)	⬆️

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