test, doc: address review suggestions for spork removal

- Update release notes to clarify that SPORK_3 and SPORK_9 were already
  effectively always enabled on mainnet but continued to gate behavior
  on test networks.
- Add explicit wait_until(IsSynced) in feature_dip3_deterministicmns
  before the getblocktemplate loop, since -budgetparams=10:10:10 sets
  superblock cycle to 10 blocks and getblocktemplate now unconditionally
  checks IsSynced() at superblock heights.
- Fix stale comment in DashTestFramework that still referenced "block
  filtering" after SPORK_3 removal.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: UdjinM6

doc/release-notes-7278.md

@@ -2,9 +2,11 @@ Removed Sporks
 --------------
 
 * `SPORK_3_INSTANTSEND_BLOCK_FILTERING` and `SPORK_9_SUPERBLOCKS_ENABLED` have
-  been removed. The behaviours they gated (InstantSend conflicting-block
-  rejection and superblock payments) are now always enabled. These sporks will
-  no longer appear in the output of the `spork` RPC.
+  been removed. These sporks were already effectively always enabled on mainnet
+  but continued to gate behavior on test networks (testnet, regtest, and devnet).
+  The associated functionality (InstantSend conflicting-block rejection and
+  superblock payments) is now permanently enabled across all networks, and the
+  sporks will no longer appear in the `spork` RPC output.
 
 Updated RPCs
 ------------

test/functional/feature_dip3_deterministicmns.py

@@ -173,6 +173,7 @@ def run_test(self):
 
         multisig = self.nodes[0].createmultisig(1, [addr1Obj['pubkey'], addr2Obj['pubkey']])['address']
         self.update_mn_payee(mns[0], multisig)
+        self.wait_until(lambda: self.nodes[0].mnsync("status")['IsSynced'])
         found_multisig_payee = False
         for _ in range(len(mns)):
             bt = self.nodes[0].getblocktemplate()

test/functional/test_framework/test_framework.py

@@ -1844,7 +1844,7 @@ def setup_network(self):
         for i in range(1, num_simple_nodes):
             force_finish_mnsync(self.nodes[i])
 
-        # Enable InstantSend (including block filtering) and ChainLocks by default
+        # Enable InstantSend and ChainLocks by default
         self.nodes[0].sporkupdate("SPORK_2_INSTANTSEND_ENABLED", 0)
         self.nodes[0].sporkupdate("SPORK_19_CHAINLOCKS_ENABLED", 0)
         self.wait_for_sporks_same()