[chore] Use grep -E in root Makefile to fix warning

[evan-bradley]

Description:

This removes a warning on recent GNU grep versions, but also works on other grep implementations. Contrib already is using the -E flag.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f37e376) 90.24% compared to head (e5a9389) 90.25%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9445      +/-   ##
==========================================
+ Coverage   90.24%   90.25%   +0.01%     
==========================================
  Files         344      344              
  Lines       17932    17932              
==========================================
+ Hits        16182    16185       +3     
+ Misses       1421     1419       -2     
+ Partials      329      328       -1     

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