[build] Use full symbols on mac64 debug trybot

NOTRY=true

Bug: chromium:822593
Change-Id: I36da13125cda8df978706a3959d9d2b66073d6eb
Reviewed-on: https://chromium-review.googlesource.com/966082Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51974}

infra/mb/mb_config.pyl

@@ -231,7 +231,7 @@
       'v8_mac_dbg': 'debug_x86_trybot',
       'v8_mac_gc_stress_dbg': 'debug_x86_trybot',
       'v8_mac64_rel': 'release_x64_trybot',
-      'v8_mac64_dbg': 'debug_x64_minimal_symbols',
+      'v8_mac64_dbg': 'debug_x64',
       'v8_mac64_asan_rel': 'release_x64_asan_no_lsan',
       'v8_linux_arm_rel_ng': 'release_simulate_arm_trybot',
       'v8_linux_arm_dbg': 'debug_simulate_arm',