Explicitly disable Gerrit tracing.performanceLogging

According to the docs [0] this shouldn't be necessary as performance
logging only happens if a performance tracing plugin is installed.
However according to this repo discuss thread [1] there is always a
dummy performanceLogging instance installed. This same thread identifies
this as a likely source for large increase in memory utilization by
Gerrit when upgrading to 3.5.

Let's explicitly disable this tracing due to the memory overhead in prep
for our 3.5 upgrade. We can always flip the setting if we install a
performance tracing plugin in our Gerrit.

[0] https://gerrit-review.googlesource.com/Documentation/config-gerrit.html#tracing
[1] https://groups.google.com/g/repo-discuss/c/QUD7_LsEVks/m/kBDEeam4AgAJ

Change-Id: Iff438695aa6488fb5886120121946494b1edf003

playbooks/roles/gerrit/templates/gerrit.config.j2

@@ -56,6 +56,8 @@
 	maxThreads = 100
 	maxQueued = 200
 	requestLog = true
+[tracing]
+	performanceLogging = false
 [cache]
 	directory = cache
 [cache "accounts"]