filesystem/resources/pbuilder/hooks/*: use /bin/bash

For consistency with the rest of PrawnOS

filesystem/resources/pbuilder/hooks/D60no-man-db-rebuild

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # Don't rebuild man-db
 
 echo "I: Preseed man-db/auto-update to false"

filesystem/resources/pbuilder/hooks/D70update

@@ -1,2 +1,2 @@
-#!/bin/sh
+#!/bin/bash
 /usr/bin/apt-get update