CompatHelper: bump compat for SpecialFunctions to 2, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the SpecialFunctions package from 0.9, 0.10, 1 to 0.9, 0.10, 1, 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 #35 (dcc80d4) into master (7820cb3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #35   +/-   ##
=======================================
  Coverage   43.31%   43.31%           
=======================================
  Files          22       22           
  Lines        3121     3121           
=======================================
  Hits         1352     1352           
  Misses       1769     1769           

---

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 7820cb3...dcc80d4. Read the comment docs.