[sl4f][e2e][audio] Increase ringbuffer size

There are situation in which we're being delayed in the 150-200ms range.
Until that situation is resolved bump the ringbuffer size 'higher than
should ever be needed'.

Test: Built+ran end to end test. CI repeatedly passing will be the final
      test.
Bug: ZX-3973
Change-Id: Ic240384192a7c418de8b37249a7379045d8e6c27