refactor: CTxMemPool::ClearPrioritisation() requires CTxMemPool::cs lock

No change in behavior, the lock is already held at call sites.
Also `const uint256` refactored to `const uint256&`.

src/txmempool.cpp

@@ -862,9 +862,9 @@ void CTxMemPool::ApplyDelta(const uint256& hash, CAmount &nFeeDelta) const
     nFeeDelta += delta;
 }
 
-void CTxMemPool::ClearPrioritisation(const uint256 hash)
+void CTxMemPool::ClearPrioritisation(const uint256& hash)
 {
-    LOCK(cs);
+    AssertLockHeld(cs);
     mapDeltas.erase(hash);
 }
 

src/txmempool.h

@@ -627,7 +627,7 @@ public:
     /** Affect CreateNewBlock prioritisation of transactions */
     void PrioritiseTransaction(const uint256& hash, const CAmount& nFeeDelta);
     void ApplyDelta(const uint256& hash, CAmount &nFeeDelta) const EXCLUSIVE_LOCKS_REQUIRED(cs);
-    void ClearPrioritisation(const uint256 hash);
+    void ClearPrioritisation(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /** Get the transaction in the pool that spends the same prevout */
     const CTransaction* GetConflictTx(const COutPoint& prevout) const EXCLUSIVE_LOCKS_REQUIRED(cs);