Shell license checks should not check the shebang (`#!`)

[bkhouri]

The license header GHA fails, unnecessarily, with the following:

❯ ../github-workflows/.github/workflows/scripts/check-license-header.sh 
--- Expected header
+++ .devcontainer/init.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh -x
 ##===----------------------------------------------------------------------===##
 ##
 ## This source file is part of the Swift open source project

It is wrong, and too restrictive, to have the "shebang" cause a license check violation.