[MB] Flip configs after Mac builder/tester split

Depends on https://crrev.com/c/3148012 to land first.

No-Try: true
Bug: chromium:1136844
Change-Id: I08b57e1d070a905dc7df71fce18891c9615a0153
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3148013Reviewed-by: Liviu Rau <liviurau@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76743}

infra/mb/mb_config.pyl

@@ -88,11 +88,10 @@
       'V8 Win64 - debug': 'debug_x64_minimal_symbols',
       'V8 Win64 - msvc': 'release_x64_msvc',
       # Mac.
-      'V8 Mac64': 'release_x64',
-      'V8 Mac64 - debug': 'debug_x64',
+      'V8 Mac64 - builder': 'release_x64',
+      'V8 Mac64 - debug builder': 'debug_x64',
       'V8 Official Mac ARM64': 'release_arm64',
       'V8 Official Mac ARM64 Debug': 'debug_arm64',
-      'V8 Mac64 GC Stress': 'debug_x64',
       'V8 Mac64 ASAN': 'release_x64_asan_no_lsan',
       'V8 Mac - arm64 - release builder': 'release_arm64',
       'V8 Mac - arm64 - debug builder': 'debug_arm64',