test(runLint): remove check for here strings

They no longer use temp files in bash 5.1+, and avoiding temp files at
all cost is not feasible maintenancewise.

Author: akinomyoga

test/runLint

@@ -72,8 +72,6 @@ gitgrep '@\([^()|$]+\)' \
 #------------------------------------------------------------------------------
 # Bash pitfalls/styles/compatibilities (which are not detected by shellcheck)
 
-gitgrep '<<<' 'herestrings use temp files, use some other way'
-
 filter_out='test/ bash_completion.sh.in' gitgrep ' \[ ' \
     'use [[ ]] instead of [ ]'