Remove obsolete aliases of WebRTC's Chromium-compile trybots

(renamed in https://chromium-review.googlesource.com/926010)

Change-Id: I3276989c8f44e32144c1989c3ee68142014a7eab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628708
Auto-Submit: Oleh Prypin <oprypin@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663365}
diff --git a/tools/mb/mb_config.pyl b/tools/mb/mb_config.pyl
index 7eb0c21c..1ca694f 100644
--- a/tools/mb/mb_config.pyl
+++ b/tools/mb/mb_config.pyl
@@ -857,10 +857,6 @@
       'mac_chromium_compile': 'gpu_tests_release_trybot',
       'linux_chromium_compile': 'release_trybot',
       'android_chromium_compile': 'android_release_trybot',
-      'win_chromium_webrtc_compile_rel_ng': 'gpu_tests_release_trybot_x86_minimal_symbols_resource_whitelisting',
-      'mac_chromium_webrtc_compile_rel_ng': 'gpu_tests_release_trybot',
-      'linux_chromium_webrtc_compile_rel_ng': 'release_trybot',
-      'android_webrtc_compile_rel': 'android_release_trybot',
     },
   },