Launch 30% of prod Buildbucket builds in "realms-aware mode".

The 5% experiment appears to be fine (based on server logs).

R=gbeaty@chromium.org
BUG=1136313

Change-Id: I716c2e9554eef0f9ee8d6b20fcea95dcc9a0bba2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2468793Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816760}

infra/config/main.star

@@ -119,7 +119,7 @@ luci.realm(
 )
 
 # Launch a portion of Swarming tasks in "realms-aware mode", crbug.com/1136313.
-luci.builder.defaults.experiments.set({"luci.use_realms": 5})
+luci.builder.defaults.experiments.set({"luci.use_realms": 30})
 
 exec("//swarming.star")