File the Fleet nav item under Assets, beside the PCs it describes

The endpoints plugin declared a section of its own, so the sidebar rendered a
one-item 'Fleet' group at the bottom, below Information, far from the PCs the
view is about. Its own docstring said it belonged just after PCs, and its
position (16, against PCs at 15) already said so too; only the section
disagreed.

Filed under assets, which puts it directly under PCs. The now-empty fleet
section is removed from NAV_SECTIONS - an unused section is an invitation to
file something else there.

plugins/endpoints/plugin.py

@@ -177,8 +177,11 @@ class EndpointsPlugin(BasePlugin):
     def get_navigation_items(self) -> List[Dict]:
         """Sidebar entry for the fleet list view.
 
-        Sits just after the PCs item (position 15) because the fleet view is
-        a telemetry lens over the same computers.
+        Filed under Assets, immediately after PCs (position 15), because the
+        fleet view is a telemetry lens over the same computers rather than a
+        different kind of thing. It shipped declaring a section of its own,
+        which rendered a one-item 'Fleet' group at the bottom of the sidebar,
+        far from the PCs it describes.
         """
         return [
             {
@@ -187,7 +190,7 @@ class EndpointsPlugin(BasePlugin):
                 'route': '/endpoints',
                 'position': 16,
                 'permission': 'endpoints.view',
-                'section': 'fleet',
+                'section': 'assets',
             },
         ]