Don't use goma for WinLibfuzzer clang ToT bot.

Looks like no other tot bot uses goma, and the bot's currently failing
since the goma client isn't available.

Bug: 903078
Change-Id: I14e9a3772f3df464d5e6549fd785b20bc10d0509
Reviewed-on: https://chromium-review.googlesource.com/c/1334272Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607766}

tools/mb/mb_config.pyl

@@ -1472,7 +1472,7 @@
       'libfuzzer', 'asan', 'release_bot', 'chrome_with_codecs', 'pdf_xfa', 'disable_nacl', 'minimal_symbols',
     ],
     'libfuzzer_windows_asan_clang_tot_release_bot': [
-      'libfuzzer', 'asan', 'clang_tot', 'release_bot', 'chrome_with_codecs', 'pdf_xfa', 'disable_nacl', 'minimal_symbols',
+      'libfuzzer', 'asan', 'clang_tot', 'release', 'chrome_with_codecs', 'pdf_xfa', 'disable_nacl', 'minimal_symbols',
     ],
     'libfuzzer_windows_asan_release_trybot': [
       'libfuzzer', 'asan', 'release_trybot', 'chrome_with_codecs', 'pdf_xfa', 'disable_nacl', 'minimal_symbols',