Fix check-headers script

Author: MaxStalker

check-headers.sh

@@ -1,8 +1,8 @@
 #!/bin/sh
 
-files=$(find . -name \*.go -type f -print0 | xargs -0 egrep -L '(Licensed under the Apache License)|(Code generated from|by)')
+files=$(find . -name \*.go -type f -print0 | xargs -0 grep -L -E '(Licensed under the Apache License)|(Code generated (from|by))')
 if [ -n "$files" ]; then
   echo "Missing license header in:"
   echo "$files"
   exit 1
-fi
+fi