CI: Remove broken pdf documentation action

[scottclowe]

See issue: ammaraskar/sphinx-action#32

[codecov]

Codecov Report

Merging #263 (1db0bbb) into master (10a6cd9) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #263   +/-   ##
=======================================
  Coverage   94.12%   94.12%           
=======================================
  Files           8        8           
  Lines        1209     1209           
  Branches      302      302           
=======================================
  Hits         1138     1138           
  Misses         36       36           
  Partials       35       35           

Flag	Coverage Δ
nbsmoke	59.88% <ø> (ø)
unittests	93.79% <ø> (ø)

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