[build] Remove configs for mac32 builders

TBR=sergiyb@chromium.org
NOTRY=true
NOTREECHECKS=true

Bug: chromium:822593
Change-Id: I86291a5039fc368c0fddea4d46e0d6c72c56a226
Reviewed-on: https://chromium-review.googlesource.com/968921
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52048}

infra/mb/mb_config.pyl

@@ -79,8 +79,6 @@
       'V8 Win64 - debug': 'debug_x64_minimal_symbols',
       'V8 Win64 - msvc': 'release_x64_msvc',
       # Mac.
-      'V8 Mac': 'release_x86',
-      'V8 Mac - debug': 'debug_x86',
       'V8 Mac64': 'release_x64',
       'V8 Mac64 - debug': 'debug_x64',
       'V8 Mac64 GC Stress': 'debug_x64',
@@ -227,10 +225,7 @@
       'v8_win64_msvc_compile_rel': 'release_x64_msvc',
       'v8_win64_dbg': 'debug_x64_minimal_symbols',
       'v8_win64_rel_ng': 'release_x64_trybot',
-      'v8_mac_rel_ng': 'release_x86_trybot',
-      'v8_mac_dbg': 'debug_x86_trybot',
       'v8_mac64_gc_stress_dbg': 'debug_x64_trybot',
-      'v8_mac64_rel': 'release_x64_trybot',
       'v8_mac64_rel_ng': 'release_x64_trybot',
       'v8_mac64_dbg': 'debug_x64',
       'v8_mac64_dbg_ng': 'debug_x64',