Fix typo (#6230)

It just a letter, but whenever you are learning, one letter can make the difference... I hope I will start contributing more and more to the project.

The typo was proxmax and not proxmox...

src: src/data/roadmaps/cyber-security/content/proxmax@jqX1A5hFF3Qznqup4lfiF.md

src/data/roadmaps/cyber-security/cyber-security.json

@@ -4203,7 +4203,7 @@
       },
       "selected": false,
       "data": {
-        "label": "proxmax",
+        "label": "proxmox",
         "style": {
           "fontSize": 17,
           "justifyContent": "flex-start",
@@ -11993,4 +11993,4 @@
       "focusable": true
     }
   ]
-}
+}