[build] Temporarily remove goma from gcov builder

This umblocks switching this builder to Xenial. The corresponding gcc
version is not yet supported by goma.

NOTRY=true

Bug: chromium:933093
Change-Id: Ib00d191c229bb598b209dcaf447321b874571e62
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1505577Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60087}

infra/mb/mb_config.pyl

@@ -434,7 +434,8 @@
     'release_x64_fuchsia_trybot': [
       'release_trybot', 'x64', 'fuchsia'],
     'release_x64_gcc_coverage': [
-      'release_bot', 'x64', 'coverage', 'gcc', 'no_custom_libcxx', 'no_sysroot'],
+      'release', 'static', 'x64', 'coverage', 'gcc', 'no_custom_libcxx',
+      'no_goma', 'no_sysroot'],
     'release_x64_internal': [
       'release_bot', 'x64', 'v8_snapshot_internal'],
     'release_x64_jumbo': [