Reduce 1mbu experimental trybot to 5% from 10% experiment.

It's been creating pages for about a week now. Decrease its experiment
percentage to avoid elevated pending times.

Bug: None
Change-Id: I0496ee591c391d1be165c43458f12e253eaa2a35
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2959596
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#892177}

infra/config/generated/commit-queue.cfg

@@ -1105,7 +1105,7 @@ config_groups {
       }
       builders {
         name: "chromium/try/linux-1mbu-compile-fyi-rel"
-        experiment_percentage: 10
+        experiment_percentage: 5
         location_regexp: ".*"
         location_regexp_exclude: ".+/[+]/docs/.+"
         location_regexp_exclude: ".+/[+]/infra/config/.+"

infra/config/generated/cq-builders.md

@@ -447,7 +447,7 @@ as required builders.
   * Experiment percentage: 1.0
 
 * [linux-1mbu-compile-fyi-rel](https://ci.chromium.org/p/chromium/builders/try/linux-1mbu-compile-fyi-rel) ([definition](https://cs.chromium.org/search?q=package:%5Echromium$+file:/cq.star$+-file:/beta/+-file:/stable/+linux-1mbu-compile-fyi-rel)) ([matching builders](https://cs.chromium.org/search?q=+file:trybots.py+linux-1mbu-compile-fyi-rel))
-  * Experiment percentage: 10.0
+  * Experiment percentage: 5.0
 
 * [linux-perfetto-rel](https://ci.chromium.org/p/chromium/builders/try/linux-perfetto-rel) ([definition](https://cs.chromium.org/search?q=package:%5Echromium$+file:/cq.star$+-file:/beta/+-file:/stable/+linux-perfetto-rel)) ([matching builders](https://cs.chromium.org/search?q=+file:trybots.py+linux-perfetto-rel))
   * Experiment percentage: 100.0

infra/config/subprojects/chromium/try.star

@@ -1156,7 +1156,7 @@ try_.chromium_linux_builder(
     builderless = False,
     goma_jobs = goma.jobs.J150,
     tryjob = try_.job(
-        experiment_percentage = 10,
+        experiment_percentage = 5,
     ),
     properties = {
         "bot_update_experiments": [