Remove sharing-peer-connection* flag metadata.

They are not used anywhere.

Change-Id: Iff2aabff98d992d987b57a326c98eb6123533139
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2414686
Commit-Queue: Richard Knoll <knollr@chromium.org>
Reviewed-by: Richard Knoll <knollr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807868}

chrome/browser/flag-metadata.json

@@ -4116,16 +4116,6 @@
     "owners": [ "//chrome/browser/sharing/OWNERS" ],
     "expiry_milestone": 86
   },
-  {
-    "name": "sharing-peer-connection-receiver",
-    "owners": [ "//chrome/browser/sharing/OWNERS" ],
-    "expiry_milestone": 88
-  },
-  {
-    "name": "sharing-peer-connection-sender",
-    "owners": [ "//chrome/browser/sharing/OWNERS" ],
-    "expiry_milestone": 88
-  },
   {
     "name": "sharing-prefer-vapid",
     "owners": [ "//chrome/browser/sharing/OWNERS" ],