[CQ] Make linux64 gcc debug bot mandatory

Bug: v8:6355
NOTRY=true
TBR=sergiyb@chromium.org

Change-Id: Ib0b6d32cf330d03d1898f55f7fc21092ce816beb
Reviewed-on: https://chromium-review.googlesource.com/503269Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45251}

infra/config/cq.cfg

@@ -46,10 +46,7 @@ verifiers {
         name: "v8_linux64_avx2_rel_ng_triggered"
         triggered_by: "v8_linux64_avx2_rel_ng"
       }
-      builders {
-        name: "v8_linux64_gcc_compile_dbg"
-        experiment_percentage: 100
-      }
+      builders { name: "v8_linux64_gcc_compile_dbg" }
       builders { name: "v8_linux64_gyp_rel_ng" }
       builders {
         name: "v8_linux64_gyp_rel_ng_triggered"