Cleanup error handling in GeoJSON and TWKB parsers

[peterstace]

Description

These could have been cleaned up in a previous PR, however the diff would have been too noisy and distracted from the more important changes there.

Check List

Have you:

• Added unit tests? N/A

• Add cmprefimpl tests? (if appropriate?) N/A

• Updated release notes? (if appropriate?) N/A

Related Issue

• Part of https://github.com/peterstace/simplefeatures/issues/504

[peterstace]

Thanks for reviewing @albertteoh , I really appreciate it 😁