Assign desktop-pwas-team@google.com as owner of PWA flags

This CL sets desktop-pwas-team@google.com to be the owner of
the following flags:
 - enable-desktop-pwas
 - enable-desktop-pwas-custom-tab-ui
 - enable-desktop-pwas-link-capturing
 - enable-desktop-pwas-stay-in-window
 - enable-experimental-app-banners
 - pwa-improved-splash-screen
 - pwa-persistent-notification

Change-Id: I06c9d53532e09ee8c9d0400d92457c248451fcb5
Reviewed-on: https://chromium-review.googlesource.com/c/1428139Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Auto-Submit: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625192}

chrome/browser/flag-metadata.json

@@ -1116,22 +1116,22 @@
   },
   {
     "name": "enable-desktop-pwas",
-    // "owners": [ "your-team" ],
+    "owners": [ "desktop-pwas-team@google.com" ],
     "expiry_milestone": 76
   },
   {
     "name": "enable-desktop-pwas-custom-tab-ui",
-    // "owners": [ "your-team" ],
+    "owners": [ "desktop-pwas-team@google.com" ],
     "expiry_milestone": 76
   },
   {
     "name": "enable-desktop-pwas-link-capturing",
-    // "owners": [ "your-team" ],
+    "owners": [ "desktop-pwas-team@google.com" ],
     "expiry_milestone": 76
   },
   {
     "name": "enable-desktop-pwas-stay-in-window",
-    // "owners": [ "your-team" ],
+    "owners": [ "desktop-pwas-team@google.com" ],
     "expiry_milestone": 76
   },
   {
@@ -1216,7 +1216,7 @@
   },
   {
     "name": "enable-experimental-app-banners",
-    // "owners": [ "your-team" ],
+    "owners": [ "desktop-pwas-team@google.com" ],
     "expiry_milestone": 76
   },
   {
@@ -2920,12 +2920,12 @@
   },
   {
     "name": "pwa-improved-splash-screen",
-    // "owners": [ "your-team" ],
+    "owners": [ "desktop-pwas-team@google.com" ],
     "expiry_milestone": 76
   },
   {
     "name": "pwa-persistent-notification",
-    // "owners": [ "your-team" ],
+    "owners": [ "desktop-pwas-team@google.com" ],
     "expiry_milestone": 76
   },
   {