test: remove redundant schema validation tests from custom-sounds

These tests validated AJV schema rejection (empty _id, regex injection via
query object/bracket syntax) which is now enforced at build time by the
new API.v1.get pattern with compiled validators.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sampaiodiego

apps/meteor/tests/end-to-end/api/custom-sounds.ts

@@ -211,10 +211,6 @@ describe('[CustomSounds]', () => {
 			await request.get(api('custom-sounds.getOne')).set(credentials).query({ _id: 'invalid-id' }).expect(404);
 		});
 
-		it('should return bad request if the _id length is not more than one', async () => {
-			await request.get(api('custom-sounds.getOne')).set(credentials).query({ _id: '' }).expect(400);
-		});
-
 		it('should return the custom sound successfully', async () => {
 			await request
 				.get(api('custom-sounds.getOne'))
@@ -230,20 +226,6 @@ describe('[CustomSounds]', () => {
 				});
 		});
 
-		it('should reject regex injection via query object', async () => {
-			await request
-				.get(api('custom-sounds.getOne'))
-				.set(credentials)
-				.query({
-					_id: { $regex: '.*' },
-				})
-				.expect(400);
-		});
-
-		it('should reject regex injection via bracket syntax', async () => {
-			await request.get(api('custom-sounds.getOne')).set(credentials).query('_id[$regex]=.*').expect(400);
-		});
-
 		it('should reject encoded regex injection attempt', async () => {
 			await request
 				.get(api('custom-sounds.getOne'))