Fix Julia icon extension lookup (#19916)

Release Notes:

- Fixed a bug where the Julia icon was not displayed for Julia files.

assets/icons/file_icons/file_types.json

@@ -84,6 +84,7 @@
     "j2k": "image",
     "java": "java",
     "jfif": "image",
+    "jl": "julia",
     "jp2": "image",
     "jpeg": "image",
     "jpg": "image",
@@ -91,7 +92,6 @@
     "json": "storage",
     "jsonc": "storage",
     "jsx": "react",
-    "julia": "julia",
     "jxl": "image",
     "kt": "kotlin",
     "ldf": "storage",