Remove Nav Target legend from app visualizer

Legacy nav-item output is no longer a first-class extension type worth
highlighting in the detailed visualizer legend.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

plugins/app-visualizer/src/components/AppVisualizerPage/DetailedVisualizer.tsx

@@ -22,12 +22,7 @@ import {
   useApi,
   routeResolutionApiRef,
   appTreeApiRef,
-  createExtensionDataRef,
 } from '@backstage/frontend-plugin-api';
-
-const legacyNavItemTargetDataRef = createExtensionDataRef<unknown>().with({
-  id: 'core.nav-item.target',
-});
 import {
   Box,
   Flex,
@@ -90,7 +85,6 @@ const getOutputColor = createOutputColorGenerator(
     [coreExtensionData.routePath.id]: '#ffeb3b',
     [coreExtensionData.routeRef.id]: '#9c27b0',
     [ApiBlueprint.dataRefs.factory.id]: '#2196f3',
-    [legacyNavItemTargetDataRef.id]: '#ff9800',
   },
 
   ['#90caf9', '#ffcc80', '#a5d6a7', '#ef9a9a', '#fff59d', '#ce93d8', '#e6ee9c'],
@@ -339,7 +333,6 @@ const legendMap = {
   'Utility API': ApiBlueprint.dataRefs.factory,
   'Route Path': coreExtensionData.routePath,
   'Route Ref': coreExtensionData.routeRef,
-  'Nav Target': legacyNavItemTargetDataRef,
 };
 
 function Legend() {