Use constant 7200 instead of TIMESTAMP_WINDOW for now

Until Bitcoin bitcoin#9908 gets backported

Author: codablock

src/wallet/test/wallet_tests.cpp

@@ -448,7 +448,7 @@ BOOST_FIXTURE_TEST_CASE(importwallet_rescan, TestChain100Setup)
 
     // Set key birthday to block time increased by the timestamp window, so
     // rescan will start at the block time.
-    const int64_t KEY_TIME = BLOCK_TIME + TIMESTAMP_WINDOW;
+    const int64_t KEY_TIME = BLOCK_TIME + 7200;
     SetMockTime(KEY_TIME);
     coinbaseTxns.emplace_back(*CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey())).vtx[0]);