Fix code scanning alerts

[jordanpadams]

Tracking issue for:

• [ ] https://github.com/NASA-PDS/validate/security/code-scanning/5
• [ ] https://github.com/NASA-PDS/validate/security/code-scanning/3
• [ ] https://github.com/NASA-PDS/validate/security/code-scanning/2
• [ ] https://github.com/NASA-PDS/validate/security/code-scanning/9
• [ ] https://github.com/NASA-PDS/validate/security/code-scanning/11
• [ ] https://github.com/NASA-PDS/validate/security/code-scanning/442

These issue are unlikely to occur, but in the event of some sort of man-in-the-middle attack, we should be extra careful here.

Note: Per comments below, this ticket is waiting on the baseline schemas/schematrons to be registered so we can use the checksums to verify we are downloading the correct files.