Fix unit test api_version to enable api_version 2 (#4785)

The command line API still uses `apiMaximumSupportedVersion`.
The unit test RPCs use `apiMinimumSupportedVersion` if unspecified.

Context:
- #4568
- #4552

src/test/jtx/impl/Env.cpp

@@ -463,7 +463,13 @@ Env::do_rpc(
     std::vector<std::string> const& args,
     std::unordered_map<std::string, std::string> const& headers)
 {
-    return rpcClient(args, app().config(), app().logs(), headers).second;
+    return rpcClient(
+               args,
+               app().config(),
+               app().logs(),
+               RPC::apiMaximumSupportedVersion,
+               headers)
+        .second;
 }
 
 void