[gm] Add 'dcheck_always_on = false' to release builds

Chrome started to enable dcheck by default in release builds that are
not official builds. Add 'dcheck_always_on = false' to release builds
in V8 to allow reasonable performance measurements.

NOTRY=true

R=jkummerow@chromium.org

Bug: v8:11879
Change-Id: I05f192fdcd5ebe5b1a82eb6f2d1648eaf6d4b527
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3048186Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75908}

tools/dev/gm.py

@@ -156,6 +156,7 @@ v8_enable_backtrace = true
 v8_enable_disassembler = true
 v8_enable_object_print = true
 v8_enable_verify_heap = true
+dcheck_always_on = false
 """.replace("{GOMA}", USE_GOMA)
 
 DEBUG_ARGS_TEMPLATE = """\