le_audio: Remove invalid tests for stopping service first

This is a follow-up CL from
https://android-review.git.corp.google.com/c/platform/packages/modules/Bluetooth/+/3085308/comments/e6c9fd25_0d21556f

Because the testing sequence doesn't match normal lifecycle of a bluetooth profile.
So the review comment suggest to remove the invalid tests, instead of
introducing changes in LeAudioService.
Those 2 test cases are causing failure when advancing leaudioUseAudioModeListener flag.

Tag: #Bug
Bug: 329172203
Flag: Exempt, test file only change
Test: atest LeAudioServiceTest LeAudioBroadcastServiceTest
Change-Id: I05307cbc62953317462c085efdf2626cd8d3df4b