Use x86 config for win32-dbg builder

This is follow up for
https://chromium.googlesource.com/chromium/src/+/7267171a528f001a5d097ea147544acb145f13e9

Bug: 867725
Change-Id: I1b8a59394acaadc4b741e7874592b090992185a5
Reviewed-on: https://chromium-review.googlesource.com/c/1350425Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610931}

tools/mb/mb_config.pyl

@@ -31,9 +31,9 @@
       'mac-rel': 'release_bot_mac_strip',
       'mac-dbg': 'debug_bot',
       'win32-rel': 'release_bot_x86_minimal_symbols_enable_archive_compression',
-      'win32-dbg': 'debug_bot',
+      'win32-dbg': 'debug_bot_x86_minimal_symbols',
       'win-rel': 'release_bot_minimal_symbols_enable_archive_compression',
-      'win-dbg': 'debug_bot',
+      'win-dbg': 'debug_bot_minimal_symbols',
     },
 
     'chromium.android': {