[code coverage] Decrease M coverage builder experiment percentage to 10%

Bug: 985581
Change-Id: Ia96e404d0b04efdeaeab703b86c4c7f4df856005
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1885026Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Yun Liu <yliuyliu@google.com>
Cr-Commit-Position: refs/heads/master@{#710099}

infra/config/buckets/try.star

@@ -207,7 +207,7 @@ android_builder(
     ssd = True,
     use_java_coverage = True,
     tryjob = tryjob(
-        experiment_percentage = 20,
+        experiment_percentage = 10,
     ),
 )
 

infra/config/generated/commit-queue.cfg

@@ -44,7 +44,7 @@ config_groups: <
       >
       builders: <
         name: "chromium/try/android-marshmallow-arm64-coverage-rel"
-        experiment_percentage: 20
+        experiment_percentage: 10
       >
       builders: <
         name: "chromium/try/android-marshmallow-arm64-rel"

infra/config/generated/cq-builders.md

@@ -322,7 +322,7 @@ by CQ. These are often used to test new configurations before they are added
 as required builders.
 
 * [android-marshmallow-arm64-coverage-rel](https://ci.chromium.org/p/chromium/builders/try/android-marshmallow-arm64-coverage-rel) ([definition](https://cs.chromium.org/search?q=package:%5Echromium$+file:/cq.star$+-file:/beta/+-file:/stable/+android-marshmallow-arm64-coverage-rel)) ([matching builders](https://cs.chromium.org/search?q=+file:trybots.py+android-marshmallow-arm64-coverage-rel))
-  * Experiment percentage: 20
+  * Experiment percentage: 10
 
 * [android-pie-arm64-rel](https://ci.chromium.org/p/chromium/builders/try/android-pie-arm64-rel) ([definition](https://cs.chromium.org/search?q=package:%5Echromium$+file:/cq.star$+-file:/beta/+-file:/stable/+android-pie-arm64-rel)) ([matching builders](https://cs.chromium.org/search?q=+file:trybots.py+android-pie-arm64-rel))
   * Experiment percentage: 50