chore: Remove duplicated tags (#4580)

## About the changes
At https://github.com/Unleash/unleash/pull/4432 we've introduced the
same tags twice which causes issues when generating the api clients.

Closes #2-1350-fix-openapi-duplicated-tags

src/lib/openapi/util/openapi-tags.test.ts

@@ -0,0 +1,8 @@
+import { openApiTags } from './openapi-tags';
+
+test('no duplicate tags', () => {
+    openApiTags.reduce((acc, tag) => {
+        expect(acc).not.toContain(tag.name);
+        return [...acc, tag.name];
+    }, []);
+});

src/lib/openapi/util/openapi-tags.ts

@@ -33,11 +33,6 @@ const OPENAPI_TAGS = [
             'Revive or permanently delete [archived feature toggles](https://docs.getunleash.io/advanced/archived_toggles).',
     },
     { name: 'Auth', description: 'Manage logins, passwords, etc.' },
-    {
-        name: 'Change Requests',
-        description:
-            'Operations related to [Change Requests](https://docs.getunleash.io/reference/change-requests).',
-    },
     {
         name: 'Client',
         description:
@@ -78,11 +73,6 @@ const OPENAPI_TAGS = [
         name: 'Metrics',
         description: 'Register, read, or delete metrics recorded by Unleash.',
     },
-    {
-        name: 'Notifications',
-        description:
-            'Manage [notifications](https://docs.getunleash.io/reference/notifications).',
-    },
     {
         name: 'Operational',
         description: