Revert "[lldb] Correct a usage after a rename was merged. (llvm#155720)"

This reverts commit de1baa5.

This is needed as the other renaming commit was reverted in
1bb8db5.

(cherry picked from commit 5f3e2b6)

Author: mstorsjo

lldb/tools/lldb-mcp/lldb-mcp.cpp

@@ -63,7 +63,7 @@ int main(int argc, char *argv[]) {
         [](MainLoopBase &loop) { loop.RequestTermination(); });
   });
 
-  auto transport_up = std::make_unique<lldb_protocol::mcp::Transport>(
+  auto transport_up = std::make_unique<lldb_protocol::mcp::MCPTransport>(
       input, output, std::string(client_name),
       [&](llvm::StringRef message) { llvm::errs() << message << '\n'; });