Remove invalid crc32 calculation

[ikreymer]

Unfortunately, the crc32 calculation that Browsertrix Crawler is doing is invalid, due to:
alexgorbatchev/crc#70
This is an easy fix, however it was added only to support stream zipping in Browsertrix.

The precalculated crc-32 is no longer needed anyway if uktrade/stream-zip#134 is merged (or we continue using our own fork in Browsertrix)

The options are:

1. Fix the crc-32 calculation
2. remove it altogether

Leaning towards removal to simplify / remove something that's not needed anymore.