Remove flag metadata for harfbuzz-pdf-subsetter

Bug: 931719
Change-Id: Idc6505c5b125768669a58109cde824b0d8e47821
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2063914
Auto-Submit: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742851}

chrome/browser/flag-metadata.json

@@ -2432,11 +2432,6 @@
     "owners": [ "steimel", "media-dev" ],
     "expiry_milestone": 84
   },
-  {
-    "name": "harfbuzz-pdf-subsetter",
-    "owners": ["dhoss", "thestig"],
-    "expiry_milestone": 80
-  },
   {
     "name": "heavy-ad-privacy-mitigations-opt-out",
     "owners": [ "johnidel", "jkarlin" ],