update bash shebang

Signed-off-by: cpanato <[email protected]>

hack/presubmit.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Copyright 2021 KO Build Authors All Rights Reserved.
 #

hack/update-codegen.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Copyright 2021 KO Build Authors All Rights Reserved.
 #

hack/update-deps.sh

@@ -1,6 +1,6 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
-# Copyright 2018 Google LLC
+# Copyright 2018 KO Build Authors All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.