perf docs: Fix man page formatting for 'perf lock'

This makes "CONTENTION" a top level section (rather than a subsection of
"INFO").

Fixes: 79079f2 ("perf lock: Add -k and -F options to 'contention' subcommand")
Reviewed-by: James Clark <[email protected]>
Signed-off-by: Nick Forrington <[email protected]>
Tested-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: NickRF

tools/perf/Documentation/perf-lock.txt

@@ -119,7 +119,7 @@ INFO OPTIONS
 
 
 CONTENTION OPTIONS
---------------
+------------------
 
 -k::
 --key=<value>::