Change all scripts #!/bin/bash -> #!/usr/bin/env bash. Also changes same

for Makefile SHELL

Signed-off-by: joshvanl <vleeuwenjoshua@gmail.com>

hack/build/print-workspace-status.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Copyright 2020 The cert-manager Authors.
 #

hack/update-gofmt.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Copyright 2020 The cert-manager Authors.
 #

test/integration/versionchecker/testdata/fetch.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Copyright 2020 The cert-manager Authors.
 #