Replace last /bin/bash with bash in test-run.sh

The other three references to bash already use "bash" instead of
"/bin/bash". Similarly, "#!/bin/bash" has already been replaced with
"#!/usr/bin/env bash".

Signed-off-by: Jonathan Wright <quaggy@gmail.com>

tests/test-run.sh

@@ -222,7 +222,7 @@ for die_with_parent_argv in "--die-with-parent" "--die-with-parent --unshare-pid
     # We have to loop here, because bwrap doesn't wait for the lock if
     # another process is holding it. If we're unlucky, lockf-n.py will
     # be holding it.
-    /bin/bash -c "while true; do $RUN ${die_with_parent_argv} --lock-file $(pwd)/lock sleep 1h; done" &
+    bash -c "while true; do $RUN ${die_with_parent_argv} --lock-file $(pwd)/lock sleep 1h; done" &
     childshellpid=$!
 
     # Wait for lock to be taken (yes hacky)