Update shebangs in installed shellscripts to meet rpmlint and match provided paths at [pkgs.org](https://fedora.pkgs.org/41/fedora-x86_64/elvish-0.21.0-4.fc41.x86_64.rpm.html)

src/shell-integration/bash/ghostty.bash

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/usr/bin/bash
 #
 # This is originally based on the recommended bash integration from
 # the semantic prompts proposal as well as some logic from Kitty's