Remove three more builders from chromium.webkit in Milo.

This removes three more entries I missed in my last two go-rounds.

TBR=hinoka@chromium.org
NOTRY=true
BUG=853040

Change-Id: I89e2397d8f0ce8b307281b0eccfae826611a8676
Reviewed-on: https://chromium-review.googlesource.com/1103715
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567903}

infra/config/global/luci-milo.cfg

@@ -1100,12 +1100,6 @@ consoles {
     category: "win|release|builder"
     short_name: "32"
   }
-  builders {
-    name: "buildbot/chromium.webkit/WebKit Win7"
-    name: "buildbucket/luci.chromium.ci/WebKit Win7"
-    category: "win|release|tester"
-    short_name: "7"
-  }
   builders {
     name: "buildbot/chromium.webkit/WebKit Win10"
     name: "buildbucket/luci.chromium.ci/WebKit Win10"
@@ -1118,18 +1112,6 @@ consoles {
     category: "mac|release"
     short_name: "bld"
   }
-  builders {
-    name: "buildbot/chromium.webkit/WebKit Mac10.10"
-    name: "buildbucket/luci.chromium.ci/WebKit Mac10.10"
-    category: "mac|release"
-    short_name: "10"
-  }
-  builders {
-    name: "buildbot/chromium.webkit/WebKit Mac10.11"
-    name: "buildbucket/luci.chromium.ci/WebKit Mac10.11"
-    category: "mac|release"
-    short_name: "11"
-  }
   builders {
     name: "buildbot/chromium.webkit/WebKit Mac10.12 (retina)"
     name: "buildbucket/luci.chromium.ci/WebKit Mac10.12 (retina)"