perf test: Fix comment ordering

The previous commit that introduced this test overlooked a behavior of
"perf test list", causing it to print "SPDX-License-Identifier: GPL-2.0"
as a description for that test.  This reorders the comments to fix that
issue.

Fixes: edf2cadf01 ("perf test: add test for BPF metadata collection")
Signed-off-by: Blake Jones <blakejones@google.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250726004023.3466563-1-blakejones@google.com
[ update the commit message a little bit ]
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/tests/shell/test_bpf_metadata.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
-# SPDX-License-Identifier: GPL-2.0
+# BPF metadata collection test
 #
-# BPF metadata collection test.
+# SPDX-License-Identifier: GPL-2.0
 
 set -e