remove bashisms from tests

tests/test-clone-r

@@ -1,4 +1,4 b''
-#!/bin/bash
+#!/bin/sh
 
 hg init test
 cd test

tests/test-push-r

@@ -1,4 +1,4 b''
-#!/bin/bash
+#!/bin/sh
 
 hg init test
 cd test