SSPKM: remove redundant ReadBlockFromDisk from IncrementNoteWitnesses.

On the latest BlockConnected/BlockDisconnected flow, the block cannot be null.

src/sapling/saplingscriptpubkeyman.cpp

@@ -203,7 +203,7 @@ void UpdateWitnessHeights(NoteDataMap& noteDataMap, int indexHeight, int64_t nWi
 }
 
 void SaplingScriptPubKeyMan::IncrementNoteWitnesses(const CBlockIndex* pindex,
-                                     const CBlock* pblockIn,
+                                     const CBlock* pblock,
                                      SaplingMerkleTree& saplingTree)
 {
     LOCK(wallet->cs_wallet);
@@ -217,17 +217,6 @@ void SaplingScriptPubKeyMan::IncrementNoteWitnesses(const CBlockIndex* pindex,
         nWitnessCacheNeedsUpdate = true;
     }
 
-    const CBlock* pblock {pblockIn};
-    CBlock block;
-    if (!pblock) {
-        if (!ReadBlockFromDisk(block, pindex)) {
-            std::string read_failed_str = strprintf("Unable to read block %d (%s) from disk.",
-                    pindex->nHeight, pindex->GetBlockHash().ToString());
-            throw std::runtime_error(read_failed_str);
-        }
-        pblock = █
-    }
-
     for (const auto& tx : pblock->vtx) {
         if (!tx->IsShieldedTx()) continue;