Small cleanups of unused code

[ponyisi]

Remove a FuncADL file left over from version 2 client, and a corresponding exception (@gordonwatts please check this isn't a problem for any of your code ...)

[codecov[bot]]

Codecov Report

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

Project coverage is 84.85%. Comparing base (7e20e9d) to head (d88afe6). Report is 28 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #515 +/- ## ========================================== + Coverage 83.90% 84.85% +0.95% ========================================== Files 26 25 -1 Lines 1485 1466 -19 ========================================== - Hits 1246 1244 -2 + Misses 239 222 -17 ``` | [Flag](https://app.codecov.io/gh/ssl-hep/ServiceX_frontend/pull/515/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssl-hep) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ssl-hep/ServiceX_frontend/pull/515/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssl-hep) | `84.85% <ø> (+0.95%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssl-hep#carryforward-flags-in-the-pull-request-comment) to find out more.

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[gordonwatts]

Changed to 3.0.1 because it is going in now