chore: Remove obsolete update-header.sh (#3174)

* chore: add MIT license information to update-header.sh

* chore: remove update-header.sh script

update-header.sh

@@ -1,7 +0,0 @@
-#!/bin/bash
-
-# Find all README.md files in subdirectories one level deep
-# and replace "### " with "## " at the beginning of lines
-find . -maxdepth 2 -type f -name "README.md" -exec sed -i '' 's/^### /## /' {} \;
-
-echo "Headers updated in README.md files."