Disable failing tab_switching.typical_25 misc story on Linux.

Looks like this was forgotten in bug 842732. Perfbot sheriff disabling
to green up tree.

Bug: 842732
Change-Id: I5affabbb0a1454dc16614efb8a70a8fd019f49e0
TBR: charliea@chromium.org
NOTRY: true
Reviewed-on: https://chromium-review.googlesource.com/1069332Reviewed-by: Annie Sullivan <sullivan@chromium.org>
Commit-Queue: Annie Sullivan <sullivan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560709}

tools/perf/expectations.config

@@ -335,6 +335,7 @@ crbug.com/843547 [ Android_Go ] system_health.memory_mobile/background:news:nyti
 
 # Benchmark: tab_switching.typical_25
 crbug.com/747026 [ Mac ] tab_switching.typical_25/multitab:misc:typical24 [ Skip ]
+crbug.com/842732 [ Linux ] tab_switching.typical_25/multitab:misc:typical24 [ Skip ]
 
 # Benchmark: thread_times.key_hit_test_cases
 crbug.com/750876 [ All ] thread_times.key_hit_test_cases/* [ Skip ]