src: fix odd linting issue

The prior commit causes a linting issue here.
Fix by changing from a struct to a class.

PR-URL: #20789
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

src/node.cc

@@ -2077,7 +2077,8 @@ node_module* get_linked_module(const char* name) {
   return FindModule(modlist_linked, name, NM_F_LINKED);
 }
 
-struct DLib {
+class DLib {
+ public:
 #ifdef __POSIX__
   static const int kDefaultFlags = RTLD_LAZY;
 #else
@@ -2098,7 +2099,7 @@ struct DLib {
 #ifndef __POSIX__
   uv_lib_t lib_;
 #endif
-
+ private:
   DISALLOW_COPY_AND_ASSIGN(DLib);
 };