flags: assign enable-horizontal-tab-switcher

Bug: None
Change-Id: I462778870e6dec251dbe942ce9d7a4c4435d0acc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1605425
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658592}

chrome/browser/flag-metadata.json

@@ -1144,8 +1144,8 @@
   },
   {
     "name": "enable-horizontal-tab-switcher",
-    // "owners": [ "your-team" ],
-    "expiry_milestone": 76
+    "owners": [ "memex-team@google.com" ],
+    "expiry_milestone": 77
   },
   {
     "name": "enable-hosted-app-quit-notification",