AudioFlinger: remove global effect enablement timeout

`kMinGlobalEffectEnabletimeNs` prevents offload track creation
whenever there was non-offloadable global effect enabled in last
20 mins.

After timer removed:
 - offload tracks can be created as long as there is no
   non-offloadable global effect enabled
 - offload tracks will be invalidated when a non-offloadable
   global effect enables

Flag: EXEMPT bug fix
Bug: 374010474
Bug: 372746934
Test: atest AudioTrackOffloadTest AudioEffectTest --iterations 10
Test: atest CtsMediaAudioTestCases
Test: Offload playback with visualizer on/off on Pixel
Change-Id: I2fb7fe98df4dc63972511efe814841668d6645d3