CompatHelper: bump compat for "SpecialFunctions" to "2"

[github-actions]

This pull request changes the compat entry for the SpecialFunctions package from 1.3 to 1.3, 2.

This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry. It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov]

Codecov Report

Merging #1249 (34253ba) into master (89d2e82) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1249   +/-   ##
=======================================
  Coverage   80.09%   80.09%           
=======================================
  Files         119      119           
  Lines        8407     8407           
=======================================
  Hits         6734     6734           
  Misses       1673     1673           

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