Fix test function code quality test to only check actual test files
Fix test function code quality test to only check actual test files

Previously it thought bin/generate_test_list.py was a test file.

Fixes #11367.

drufat/sympy,kaushik94/sympy,jaimahajan1997/sympy,souravsingh/sympy,yashsharan/sympy,jaimahajan1997/sympy,yashsharan/sympy,sampadsaha5/sympy,skidzo/sympy,skidzo/sympy,chaffra/sympy,madan96/sympy,chaffra/sympy,jaimahajan1997/sympy,madan96/sympy,aktech/sympy,souravsingh/sympy,postvakje/sympy,skidzo/sympy,sampadsaha5/sympy,aktech/sympy,kaushik94/sympy,aktech/sympy,yashsharan/sympy,postvakje/sympy,drufat/sympy,souravsingh/sympy,kaushik94/sympy,chaffra/sympy,sampadsaha5/sympy,postvakje/sympy,drufat/sympy,madan96/sympy