Remove internal timeout from `get_segment_slice_async`

**Problem description**
Currently there is a timeout internal to `get_segment_slice_async` this causes problems with some of the integration tests. For example:
https://github.com/pravega/pravega-client-rust/runs/7682183505?check_suite_focus=true

**Problem location**
Reader.aquire_segmnet

**Suggestions for an improvement**
Remove the timeout an allow the caller to wait as long as needed.