hack: update shebang (zalando#755)

zimbatm · erthalion · commit 076116589d88 · 2019-12-10T14:54:12.000+01:00
Make the shebang work on NixOS and other non-Ubuntu systems.
diff --git a/hack/update-codegen.sh b/hack/update-codegen.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -o errexit
 set -o nounset
diff --git a/hack/verify-codegen.sh b/hack/verify-codegen.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -o errexit
 set -o nounset
