Don't log every single node being replaced when node defs refreshed (#918)

Currently, when node defs are refreshed (e.g., by pressing "r"
shortcut), every single node def is logged, which is useless when
there's hundred of nodes and clutters console. This PR changes to only
log those messages when in debug mode.

src/LiteGraphGlobal.ts

@@ -299,7 +299,7 @@ export class LiteGraphGlobal {
     }
 
     const prev = this.registered_node_types[type]
-    if (prev) {
+    if (prev && this.debug) {
       console.log("replacing node type:", type)
     }