.coveragerc: use globs with includes

[blueyed]

Apparently this causes missing coverage with pdb/pexpect tests.

Ref: #4865 (comment)

[codecov]

Codecov Report

Merging #4867 into master will increase coverage by 0.25%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4867      +/-   ##
==========================================
+ Coverage   94.29%   94.54%   +0.25%     
==========================================
  Files         113      113              
  Lines       25172    25172              
  Branches     2499     2499              
==========================================
+ Hits        23735    23798      +63     
+ Misses       1100     1047      -53     
+ Partials      337      327      -10

Impacted Files	Coverage Δ
src/_pytest/assertion/rewrite.py	95.47% <0%> (+0.16%)	⬆️
src/_pytest/warnings.py	88.88% <0%> (+1.23%)	⬆️
src/_pytest/config/__init__.py	93.8% <0%> (+1.63%)	⬆️
src/_pytest/terminal.py	91.74% <0%> (+2.64%)	⬆️
src/_pytest/debugging.py	60.37% <0%> (+3.14%)	⬆️
src/_pytest/capture.py	93.7% <0%> (+3.82%)	⬆️
src/_pytest/helpconfig.py	97.29% <0%> (+11.71%)	⬆️

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