Windows shebang potential fix? (#2957)

# Description and Motivation
<!--- bulleted, high level items. use keywords (eg "closes #144" or
"fixes #4323") -->

Hopefully correctly setting the `sh` at the she bang atop the script
file might help with windows compatibility issues

scripts/.util/warn_many_files_per_commit.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 # Get the list of files to be committed
 files=$(git diff --cached --name-only)