Drop Batch impl. of Git hook (shim) as it's apparently not used

see ffa5bb9b7
this should now work in Git BASH as well
and it wasn't all for nothing, at least now I have reference for a
polyglot if the need arises

Dist/git_hook_shims/commit-msg

@@ -1,12 +1,3 @@
-@{a="\"} >$null # " 2>/dev/null || true #" >NUL 2>&1 || TYPE NUL & ECHO OFF
-
-echo \" <<'BATCH_SCRIPT' >/dev/null ">NUL "\"
-dotnet pwsh .\Dist\git_hooks\commit-msg.ps1 %*
-GOTO :eof
-BATCH_SCRIPT
-# else this is BASH
-# heredoc trick for polyglot taken from https://github.com/llamasoft/polyshell#how-it-works -- this script is basically that sans PowerShell support (since that's not the shell on Windows)
-# improved Batch `ECHO OFF` taken from https://github.com/tingstad/polyscript#explanation
-
+#!/bin/sh
+set -e
 dotnet pwsh "./Dist/git_hooks/$(basename "$0").ps1" "$@"
-exit $?