Remove unused config for HFP Connection Service

The config "hfp_client_connection_service" is only used in HfpClientConnectionServiceTest, and is blocking the test from running. To increase test coverage, config is removed.

Bug: 237467631
Test: atest HfpClientConnectionServiceTest
Change-Id: I58887c18bc3b7a13747affaff062907796f763d5
Merged-In: I58887c18bc3b7a13747affaff062907796f763d5
(cherry picked from commit c00a3c12)