Update for Python 3.9+, deprecate Reppy dependency

[rivermont]

Reppy doesn't work past Python 3.8 - seomoz/reppy#122, seomoz/reppy#132 - which means our robots.txt parser isn't working (#81).
Python 3.8 also reaches end-of-life next year so this needs to happen anyway.

• Branch without any robots parser
• Find replacement robots parser
• Test whole program for 3.9-3.11 compatibility

[trs-eric]

Confirmed on Debian 12.

[rivermont]

Will replace reppy with scrapy/protego