instance of 'mem pool' to 'mempool'

there was only one instance of  'mem pool' and not 'mempool', so I changed it to conform to the others

src/rpc/blockchain.cpp

@@ -863,7 +863,7 @@ UniValue gettxout(const JSONRPCRequest& request)
             "\nArguments:\n"
             "1. \"txid\"       (string, required) The transaction id\n"
             "2. n              (numeric, required) vout number\n"
-            "3. includemempool  (boolean, optional) Whether to include the mem pool\n"
+            "3. includemempool  (boolean, optional) Whether to include the mempool\n"
             "\nResult:\n"
             "{\n"
             "  \"bestblock\" : \"hash\",    (string) the block hash\n"

src/rpc/mining.cpp

@@ -230,7 +230,7 @@ UniValue getmininginfo(const JSONRPCRequest& request)
             "  \"difficulty\": xxx.xxxxx    (numeric) The current difficulty\n"
             "  \"errors\": \"...\"            (string) Current errors\n"
             "  \"networkhashps\": nnn,      (numeric) The network hashes per second\n"
-            "  \"pooledtx\": n              (numeric) The size of the mem pool\n"
+            "  \"pooledtx\": n              (numeric) The size of the mempool\n"
             "  \"chain\": \"xxxx\",           (string) current network name as defined in BIP70 (main, test, regtest)\n"
             "}\n"
             "\nExamples:\n"