Add final newline to pre-push githook script

I think that I added this script via some automated process, and I guess
that unfortunately that automated process failed to include a final
newline at the end of the file. Adding one now.

bin/githooks/pre-push

@@ -2,4 +2,4 @@
 
 set -euo pipefail # exit on any error, don't allow undefined variables, pipes don't swallow errors
 
-lint gitleaks
+lint gitleaks