sched/balancing: Change comment formatting to not overlap Git conflict marker lines

So the scheduler has two such comment blocks, with '=' used as a double underline:

        /*
         * VRUNTIME
         * ========
         *

'========' also happens to be a Git conflict marker, throwing off a simple
search in an editor for this pattern.

Change them to '-------' type of underline instead - it looks just as good.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240308105901.1096078-7-mingo@kernel.org