[Coverage] Make coverage a 100% experiment

BUG=chromium:568949
LOG=n
TBR=kjellander@chromium.org, tandrii@chromium.org
NOTRY=true
NOPRESUBMIT=true

Review URL: https://codereview.chromium.org/1830153002

Cr-Commit-Position: refs/heads/master@{#35057}

infra/config/cq.cfg

@@ -71,7 +71,7 @@ verifiers {
       }
       builders {
         name: "v8_linux64_sanitizer_coverage_rel"
-        experiment_percentage: 30
+        experiment_percentage: 100
       }
     }
   }