Fix regex to deal with mixing of quotes at start of string

[DanielNoord]

Closes #489

I guess that regex was always doomed to fail.

This should fix it. There are some weird changes that I don't particularly like.

For example, capitalization in """'A.m.' or 'p.m.'.""" is not desired I think...
Also """"""a.m.""" or "p.m.".""" is invalid syntax.

However, we have always said that we can't format everything perfectly and "crap in is crap out". Since this at least fixes the bug I think it is still an improvement.

[github-actions]

According to the primer, this change has no effect on the checked open source code. 🤖🎉

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (13d4261) to head (f40b910).
⚠️ Report is 31 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #491   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
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  Files           31        31           
  Lines         1126      1126           
  Branches       120       120           
=========================================
  Hits          1126      1126           

Flag	Coverage Δ
linux	98.93% <100.00%> (ø)
windows	100.00% <100.00%> (ø)

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Files with missing lines	Coverage Δ
pydocstringformatter/_formatting/base.py	100.00% <100.00%> (ø)

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[DanielNoord]

#493 fixes the 'A.m.' formatting