[CODEOWNERS] fix appex-qa ownership (elastic#189602)

## Summary

I noticed `elastic/appex-qa` is pinged for quite many PRs.

with elastic#188606 some test folders became packages with `"owner":
"@elastic/appex-qa",`, that autmatically updated CODEOWNERS file with
appex-qa listed for basically every test path.


https://github.com/elastic/kibana/pull/188606/files#diff-3d36a1bf06148bc6ba1ce2ed3d19de32ea708d955fed212c0d27c536f0bd4da7R878-R881

This PR removes `owner` for the following test "packages"
- x-pack/test_serverless 
- test 
- x-pack/test 

and CODEOWNERS file keeps these paths without specific owner.

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>

.github/CODEOWNERS

@@ -875,9 +875,9 @@ packages/kbn-test-eui-helpers @elastic/kibana-visualizations
 x-pack/test/licensing_plugin/plugins/test_feature_usage @elastic/kibana-security
 packages/kbn-test-jest-helpers @elastic/kibana-operations @elastic/appex-qa
 packages/kbn-test-subj-selector @elastic/kibana-operations @elastic/appex-qa
-x-pack/test_serverless @elastic/appex-qa
-test @elastic/appex-qa
-x-pack/test @elastic/appex-qa
+x-pack/test_serverless 
+test 
+x-pack/test 
 x-pack/performance @elastic/appex-qa
 x-pack/examples/testing_embedded_lens @elastic/kibana-visualizations
 packages/kbn-text-based-editor @elastic/kibana-esql
@@ -1263,7 +1263,6 @@ x-pack/test/observability_ai_assistant_functional @elastic/obs-ai-assistant
 /test/functional/services/remote @elastic/appex-qa
 /test/visual_regression @elastic/appex-qa
 /x-pack/test/visual_regression @elastic/appex-qa
-/x-pack/performance @elastic/appex-qa
 /packages/kbn-test/src/functional_test_runner @elastic/appex-qa
 /packages/kbn-performance-testing-dataset-extractor @elastic/appex-qa
 /x-pack/test_serverless/**/*config.base.ts @elastic/appex-qa
@@ -1273,7 +1272,7 @@ x-pack/test/observability_ai_assistant_functional @elastic/obs-ai-assistant
 /x-pack/test_serverless/api_integration/test_suites/common/elasticsearch_api @elastic/appex-qa
 /x-pack/test_serverless/functional/test_suites/security/ftr/ @elastic/appex-qa
 /x-pack/test_serverless/functional/test_suites/common/home_page/  @elastic/appex-qa
-/x-pack/test_serverless/functional/services/ @elastic/appex-qa
+/x-pack/test_serverless/**/services/ @elastic/appex-qa
 
 # Core
 /config/ @elastic/kibana-core

test/kibana.jsonc

@@ -1,6 +1,6 @@
 {
   "type": "test-helper",
   "id": "@kbn/test-suites-src",
-  "owner": "@elastic/appex-qa",
+  "owner": [],
   "devOnly": true
 }

x-pack/test/kibana.jsonc

@@ -1,6 +1,6 @@
 {
   "type": "test-helper",
   "id": "@kbn/test-suites-xpack",
-  "owner": "@elastic/appex-qa",
+  "owner": [],
   "devOnly": true
 }

x-pack/test_serverless/kibana.jsonc

@@ -1,6 +1,6 @@
 {
   "type": "test-helper",
   "id": "@kbn/test-suites-serverless",
-  "owner": "@elastic/appex-qa",
+  "owner": [],
   "devOnly": true
 }