Fix typo in WebRTC config.

Bug: 877018
Change-Id: I3502e8ce9c8410f3af1c52581adbc0d708806a7f
Reviewed-on: https://chromium-review.googlesource.com/1245365Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Commit-Queue: Patrik Höglund <phoglund@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594601}

infra/config/global/luci-scheduler.cfg

@@ -4660,7 +4660,7 @@ job {
   buildbucket: {
     server: "cr-buildbucket.appspot.com"
     bucket: "luci.chromium.webrtc.fyi"
-    builder: "WebRTC Chromium FYI Win8 Tester"
+    builder: "WebRTC Chromium FYI Win7 Tester"
   }
 }