[wallet] Remove importmulti always-true check

Remove "nLowestTimestamp <= chainActive.Tip()->GetBlockTimeMax()" check from
importmulti, which is always true because nLowestTimestamp is set to the
minimum of the most recent block time and all the imported key timestamps,
which is necessarily lower than the maximum block time.

src/wallet/rpcdump.cpp

@@ -1072,7 +1072,7 @@ UniValue importmulti(const JSONRPCRequest& mainRequest)
         }
     }
 
-    if (fRescan && fRunScan && requests.size() && nLowestTimestamp <= chainActive.Tip()->GetBlockTimeMax()) {
+    if (fRescan && fRunScan && requests.size()) {
         CBlockIndex* pindex = nLowestTimestamp > minimumTimestamp ? chainActive.FindEarliestAtLeast(std::max<int64_t>(nLowestTimestamp - 7200, 0)) : chainActive.Genesis();
 
         if (pindex) {