scripted-diff: rename CBasicKeyStore to FillableSigningProvider

-BEGIN VERIFY SCRIPT-
git grep -l "CBasicKeyStore" | xargs sed -i -e 's/CBasicKeyStore/FillableSigningProvider/g'
-END VERIFY SCRIPT-

src/rpc/misc.cpp

@@ -122,7 +122,7 @@ static UniValue createmultisig(const JSONRPCRequest& request)
     }
 
     // Construct using pay-to-script-hash:
-    CBasicKeyStore keystore;
+    FillableSigningProvider keystore;
     CScript inner;
     const CTxDestination dest = AddAndGetMultisigDestination(required, pubkeys, output_type, keystore, inner);