test: Remove no longer needed MakeChain calls

These calls are no longer needed after edc316020e
from #19098 which started instantiating BasicTestingSetup.m_node.chain

Patch from MarcoFalke <falke.marco@gmail.com> in
https://github.com/bitcoin/bitcoin/pull/19425#discussion_r526701954

Co-authored-by: MarcoFalke <falke.marco@gmail.com>

src/wallet/test/scriptpubkeyman_tests.cpp

@@ -17,9 +17,7 @@ BOOST_FIXTURE_TEST_SUITE(scriptpubkeyman_tests, BasicTestingSetup)
 BOOST_AUTO_TEST_CASE(CanProvide)
 {
     // Set up wallet and keyman variables.
-    NodeContext node;
-    std::unique_ptr<interfaces::Chain> chain = interfaces::MakeChain(node);
-    CWallet wallet(chain.get(), "", CreateDummyWalletDatabase());
+    CWallet wallet(m_node.chain.get(), "", CreateDummyWalletDatabase());
     LegacyScriptPubKeyMan& keyman = *wallet.GetOrCreateLegacyScriptPubKeyMan();
 
     // Make a 1 of 2 multisig script