test: replace v28.0 with notarized v28.2

Since #31407 guix builds are signed and notarized. This was backported to v28, so bump the version.

test/functional/wallet_migration.py

@@ -52,7 +52,7 @@ class WalletMigrationTest(BitcoinTestFramework):
             extra_args=self.extra_args,
             versions=[
                 None,
-                280000,
+                280200,
             ],
         )
         self.start_nodes()