[ObjC] remove grpc_bazel_cpp_ios_event_engine_experiment_tests (#35283)

zero cases ran according to CI logs:
e.g.:
```
Executing tests from //test/core/event_engine/cf:cf_engine_test_on_ios
-----------------------------------------------------------------------------
2023-12-09 21:28:59,623 Creating a new simulator:
Name: New-iPhone X-16.1
OS: iOS 16.1
Type: iPhone X
2023-12-09 21:29:00,377 Created new simulator 9958E216-2526-4A95-A70F-8E006D6DB512.
2023-12-09 21:29:01,105 Will consider the test as test type logic_test to run.
Test Suite 'All tests' started at 2023-12-09 13:29:01.708
Test Suite 'All tests' passed at 2023-12-09 13:29:01.709.
	 Executed 0 tests, with 0 failures (0 unexpected) in 0.000 (0.001) seconds
2023-12-09 21:29:01,715 Deleting simulator 9958E216-2526-4A95-A70F-8E006D6DB512 asynchronously.
2023-12-09 21:29:01,720 Done.
```

All logs in:
https://source.cloud.google.com/results/invocations/f77ffe5d-d5c8-4aea-a54d-80e02c7d54fd/targets/grpc%2Fcore%2Fpull_request%2Fmacos%2Fgrpc_bazel_cpp_ios_event_engine_experiment_tests/log
https://source.cloud.google.com/results/invocations/2a12c3be-1f7c-48af-8a2d-26982a72c04b/targets
https://source.cloud.google.com/results/invocations/2a12c3be-1f7c-48af-8a2d-26982a72c04b/targets/%2F%2Ftest%2Fcore%2Fevent_engine%2Fcf:cf_engine_test_on_ios/log

-----
PS: although no tests were executed, we are seeing random timeouts in the internal CI most likely due to the environment issue as tests are still being build and emulators are being lunched.

Closes #35283

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35283 from HannahShiSFB:remove-grpc_bazel_cpp_ios_event_engine_experiment_tests c149b4eb39
PiperOrigin-RevId: 590792491

tools/internal_ci/macos/pull_request/grpc_bazel_cpp_ios_event_engine_experiment_tests.cfg

@@ -1,42 +0,0 @@
-# Copyright 2023 The gRPC Authors
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# Config file for the internal CI (in protobuf text format)
-
-# Location of the continuous shell script in repository.
-build_file: "grpc/tools/internal_ci/macos/grpc_run_bazel_cpp_ios_tests.sh"
-timeout_mins: 90
-action {
-  define_artifacts {
-    regex: "**/*sponge_log.*"
-    regex: "github/grpc/reports/**"
-  }
-}
-
-gfile_resources: "/bigstore/grpc-testing-secrets/gcp_credentials/GrpcTesting-d0eeee2db331.json"
-gfile_resources: "/bigstore/grpc-testing-secrets/gcp_credentials/resultstore_api_key"
-
-bazel_setting {
-  # In order for Kokoro to recognize this as a bazel build and publish the bazel resultstore link,
-  # the bazel_setting section needs to be present and "upsalite_frontend_address" needs to be
-  # set. The rest of configuration from bazel_setting is unused (we configure everything when bazel
-  # command is invoked).
-  upsalite_frontend_address: "https://source.cloud.google.com"
-}
-
-env_vars {
-  # flags will be passed to bazel invocation
-  key: "BAZEL_FLAGS"
-  value: "--config=dbg --cxxopt=-DGRPC_IOS_EVENT_ENGINE_CLIENT=1"
-}