UI: Tweak extensions repository panel

Reduce the width size and align the URL with the UIList.

Adjustments that would still be welcome:
* Make URL label color the same as Advanced.
* Waste less space between URL and the [________________].

scripts/startup/bl_ui/space_userpref.py

@@ -2025,7 +2025,7 @@ class USERPREF_PT_extensions_repos(Panel):
     bl_region_type = 'HEADER'
 
     # Show wider than most panels so the URL & directory aren't overly clipped.
-    bl_ui_units_x = 24
+    bl_ui_units_x = 16
 
     # NOTE: ideally `if panel := layout.panel("extensions_repo_advanced", default_closed=True):`
     # would be used but it isn't supported here, use a kludge to achieve a similar UI.
@@ -2082,8 +2082,6 @@ class USERPREF_PT_extensions_repos(Panel):
         if active_repo is None:
             return
 
-        layout.separator()
-
         # NOTE: changing repositories from remote to local & vice versa could be supported but is obscure enough
         # that it can be hidden entirely. If there is a some justification to show this, it can be exposed.
         # For now it can be accessed from Python if someone is.
@@ -2091,9 +2089,11 @@ class USERPREF_PT_extensions_repos(Panel):
 
         if active_repo.use_remote_path:
             row = layout.row()
+            split = row.split(factor=0.936)
             if active_repo.remote_path == "":
-                row.alert = True
-            row.prop(active_repo, "remote_path", text="URL")
+                split.alert = True
+            split.prop(active_repo, "remote_path", text="URL")
+            split = row.split()
 
         if layout_panel := self._panel_layout_kludge(layout, text="Advanced"):