Bump linux-libfuzzer-asan-rel's CQ experiment to 50%.

It appears to have enough bots. Will bump more if needed.

TBR=jbudorick@chromium.org

Bug: 646404
Change-Id: I4046177c2adb2916ec293cc1961753577739e4c9
Reviewed-on: https://chromium-review.googlesource.com/1220703Reviewed-by: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590510}

infra/config/branch/cq.cfg

@@ -74,7 +74,7 @@ verifiers {
       # TODO(crbug.com/646404): Scale this up to 100% mandatory.
       builders {
         name: "linux-libfuzzer-asan-rel"
-        experiment_percentage: 10
+        experiment_percentage: 50
       }
       builders { name: "linux-ozone-rel" }
       builders { name: "linux_chromium_compile_dbg_ng" }