doc: fix file name to main.mjs and not main.js in esm.md

PR-URL: #34786
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Derek Lewis <[email protected]>
Reviewed-By: Geoffrey Booth <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Rich Trott <[email protected]>

Author: frank-dspeed

doc/api/esm.md

@@ -1506,8 +1506,8 @@ console.log(VERSION);
 
 With this loader, running:
 
-```console
-node --experimental-loader ./https-loader.mjs ./main.js
+```bash
+node --experimental-loader ./https-loader.mjs ./main.mjs
 ```
 
 Will print the current version of CoffeeScript per the module at the URL in