perf: remove duplicated check of same key in the instant send database

Previous implementation checked both Deterministic and Non-deterministic
instant send locks; though once non-determinstic has been removed,
implementation has been updated and now the same key is checked twice.

This commit removes duplicated check

Author: knst

src/instantsend/db.cpp

@@ -279,11 +279,7 @@ InstantSendLockPtr CInstantSendDb::GetInstantSendLockByHashInternal(const uint25
     ret = std::make_shared<InstantSendLock>();
     bool exists = db->Read(std::make_tuple(DB_ISLOCK_BY_HASH, hash), *ret);
     if (!exists || (::SerializeHash(*ret) != hash)) {
-        ret = std::make_shared<InstantSendLock>();
-        exists = db->Read(std::make_tuple(DB_ISLOCK_BY_HASH, hash), *ret);
-        if (!exists || (::SerializeHash(*ret) != hash)) {
-            ret = nullptr;
-        }
+        ret = nullptr;
     }
     islockCache.insert(hash, ret);
     return ret;