Update MILO entry of linux-builder-perf and remove the legacy 'Linux Builder...

Update MILO entry of linux-builder-perf and remove the legacy 'Linux Builder Perf' config in mb_config.pyl

Bug: 828467
Change-Id: I93df365ccf16e9668fd7fd07b79bbff8646311c9
Reviewed-on: https://chromium-review.googlesource.com/1206930Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#588966}

infra/config/global/luci-milo.cfg

@@ -1264,8 +1264,7 @@ consoles {
     short_name: "mac"
   }
   builders {
-    name: "buildbot/chromium.perf/Linux Builder Perf"
-    name: "buildbucket/luci.chrome.ci/Linux Builder Perf"
+    name: "buildbucket/luci.chrome.ci/linux-builder-perf"
     category: "builder"
     short_name: "lnx"
   }

tools/mb/mb_config.pyl

@@ -382,8 +382,6 @@
       'Android Compile Perf': 'official_goma_minimal_symbols_android',
       'Android arm64 Compile Perf': 'official_goma_minimal_symbols_android_arm64',
       'android-builder-perf': 'official_goma_minimal_symbols_android',
-      # TODO(crbug.com/828467): Remove 'Linux Builder Perf'
-      'Linux Builder Perf': 'official_goma_perf',
       'linux-builder-perf': 'official_goma_perf',
       # TODO(crbug.com/828468): Remove 'Mac Builder Perf'
       'Mac Builder Perf': 'official_goma',