Remove reference to old gn win x64 bot in roll_gn.py.

R=brettw@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/1947123004
Cr-Original-Commit-Position: refs/heads/master@{#391701}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: aec64c190cd89a0bc5e933fe96fc9a3641e29d7b
diff --git a/tools/gn/bin/roll_gn.py b/tools/gn/bin/roll_gn.py
index 10b218c..b15aaf0 100755
--- a/tools/gn/bin/roll_gn.py
+++ b/tools/gn/bin/roll_gn.py
@@ -432,8 +432,7 @@
       '\n'
       'TBR=%s\n'
       'CQ_EXTRA_TRYBOTS=tryserver.chromium.mac:mac_chromium_gn_dbg;'
-      'tryserver.chromium.win:win8_chromium_gn_dbg,'
-      'win_chromium_gn_x64_rel\n' % (
+      'tryserver.chromium.win:win8_chromium_gn_dbg\n' % (
         old_buildtools_commitish[:COMMITISH_DIGITS],
         new_buildtools_commitish[:COMMITISH_DIGITS],
         self.old_gn_commitish[:COMMITISH_DIGITS],