Import `json` directly

[k12ish]

Description

Removes warning in pylib/anki/utils.py line 42 (link): Its an admittedly minor issue, but printing the traceback is something that clutters the terminal up when building and running anki.

Checklist:

• [x] I've read and understood the contribution guidelines
• [x] I've tested my changes against at least one of the following Anki builds:
  • [x] Latest standard Anki 2.1 binary build [required for Anki-compatible 2.1 add-ons]
  • [ ] Latest alternative Anki 2.1 binary build
  • [ ] Latest Anki 2.0 binary build [required for Anki 2.0-compatible add-ons]
• [x] I've tested my changes on at least one of the following platforms:
  • [x] Linux, version: Ubuntu LTS
  • [ ] Windows, version:
  • [ ] macOS, version:
• [ ] My changes potentially affect non-desktop platforms, of which I've tested:
  • [ ] AnkiMobile, version:
  • [ ] AnkiDroid, version:
  • [ ] AnkiWeb

[glutanimate]

Thanks, appreciate it!