[Telemetry] Disable memory_pressure to match old master.cfg.

It was unintentionally enabled with the switch to recipes.

BUG=388885
TBR=dtu@chromium.org
NOTRY=True

Review URL: https://codereview.chromium.org/596483002

Cr-Commit-Position: refs/heads/master@{#295979}

tools/perf/benchmarks/memory_pressure.py

@@ -7,7 +7,7 @@ from measurements import memory_pressure
 import page_sets
 
 
-@benchmark.Enabled('has tabs')
+@benchmark.Disabled
 class MemoryPressure(benchmark.Benchmark):
   test = memory_pressure.MemoryPressure
   page_set = page_sets.Typical25PageSet