test: Don't be unnecessarily noisy in this test

This is confusing if you're looking for an error in the test.

test/shell/file-move.sh

@@ -1,7 +1,7 @@
 #!/bin/bash -e
 
 mkdir -p /tmp/mgmt/
-rm /tmp/mgmt/f1 || true
+rm /tmp/mgmt/f1 &>/dev/null || true
 
 # run empty graph, with prometheus support
 $timeout --kill-after=60s 55s "$MGMT" run --tmp-prefix yaml --yaml=file-move.yaml 2>&1 | tee /tmp/mgmt/file-move.log &