Removing unused fields from ReaderSettings

[Myllyenko]

Removing unused fields to avoid misconfiguration of a reader.

• Looks like maxLag and readFrom were added to ReaderSettings by mistake because they belong to TopicReadSettings.
• decompress is unused at least for now.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 47.38%. Comparing base (959538e) to head (c0d89f5).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #337 +/- ## ============================================ + Coverage 47.34% 47.38% +0.04% Complexity 1750 1750 ============================================ Files 309 309 Lines 12463 12448 -15 Branches 1232 1232 ============================================ - Hits 5901 5899 -2 + Misses 6102 6089 -13 Partials 460 460 ```

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[pnv1]

Thank you for noticing! It's really better to just remove these options until they are used in any way