Revert "Raise linux_chromium_ozone_compile_ng cq experiment from 10% to 50%"

This reverts commit 9dcd8a50.

Reason for revert: This overloads the slaves in the group.

Bug: 805771

Original change's description:
> Raise linux_chromium_ozone_compile_ng cq experiment from 10% to 50%
>
> Bot is stable over the past months.
> BUG=694033
>
> Change-Id: I2f383da545eb39c4745a7cb18e35473f7aa62300
> Reviewed-on: https://chromium-review.googlesource.com/793472
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
> Cr-Commit-Position: refs/heads/master@{#531503}

TBR=dpranke@chromium.org,tonikitoo@igalia.com

Change-Id: Ifdca60a3a76c71c1433dca88a5bb278b9165c85a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 694033
Reviewed-on: https://chromium-review.googlesource.com/884556Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531783}

infra/config/cq.cfg

@@ -94,7 +94,7 @@ verifiers {
       }
       builders {
         name: "linux_chromium_ozone_compile_only_ng"
-        experiment_percentage: 50
+        experiment_percentage: 10
       }
       builders {
         name: "linux_chromium_compile_dbg_ng"