chore: drop three reads whose result went nowhere

The requirement parser read core, hashMatchMandatory and note from
each bios element and discarded all three, which reads like a dropped
attribute: hashMatchMandatory decides whether a wrong hash is yellow or
red on Recalbox. It is not lost -- the config parser below captures it
for the YAML -- so these were leftovers, and they cost a look to
confirm that.

Two yaml imports left unused by the move to the shared loader go too.

scripts/scraper/batocera_scraper.py

@@ -16,7 +16,6 @@ import urllib.error
 import urllib.request
 from pathlib import Path
 
-import yaml
 
 from common import yaml_load