Fix bad builder configuration.

We agreed to use a standard sized machine for tester.

TBR=smut,nodir

Bug: 897407
Change-Id: I9579001261f36e3b86dd92c154b65873e4116735
Reviewed-on: https://chromium-review.googlesource.com/c/1298491Reviewed-by: Roberto Carrillo <robertocn@chromium.org>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Reviewed-by: smut <smut@google.com>
Commit-Queue: Roberto Carrillo <robertocn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602532}

infra/config/global/cr-buildbucket.cfg

@@ -1862,7 +1862,7 @@ buckets {
     builders {
       name: "linux-code-coverage-tester"
       mixins: "code-coverage"
-      dimensions: "cores:32"
+      dimensions: "cores:8"
     }
 
     builders {