Update microsite/sidebars.ts to remove .md on some pages

Co-authored-by: Aramis Sennyey <159921952+aramissennyeydd@users.noreply.github.com>
Signed-off-by: milliehartnt123 <108491788+milliehartnt123@users.noreply.github.com>

microsite/sidebars.ts

@@ -55,9 +55,9 @@ export default {
         label: 'Using Backstage',
         items: [
           'getting-started/logging-in',
-          'getting-started/viewing-catalog.md',
-          'getting-started/view-what-you-own.md',
-          'getting-started/viewing-entity-relationships.md',
+          'getting-started/viewing-catalog',
+          'getting-started/view-what-you-own',
+          'getting-started/viewing-entity-relationships',
           {
             type: 'category',
             label: 'Managing Components',