Remove Keybase integration (#17045)

db/post_migrate/20211126000907_drop_account_identity_proofs.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class DropAccountIdentityProofs < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def up
+    drop_table :account_identity_proofs
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end