[go/perfbot-sheriff][base_perftests] Properly disable NotifyPerformance

This change should be committed right away per go/perfbot-sheriff
since this is failing on the waterfall.

r610618 didn't work since
TYPED_TEST(ObserverListPerfTest, MAYBE_NotifyPerformance) {
is preprocessed to
something_MAYBE_NotifyPerformance
So then the directive
#define MAYBE_NotifyPerformance DISABLED_NotifyPerformance
is not applied.

This will fix both 908490 and 906686.

Bug: 906686,908490
Change-Id: Ib2adc016fbef79bb889a076e452534f893fb09b5
Reviewed-on: https://chromium-review.googlesource.com/c/1352481
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: John Rummell <jrummell@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611397}
1 file changed