[FastAPI] Jinja contextfilter renamed to pass_context

aurweb/util.py:88
  /builds/kevr/aurweb/aurweb/util.py:88: DeprecationWarning: 'contextfilter' is renamed to 'pass_context', the old name will be removed in Jinja 3.1.
    def account_url(context, user):
aurweb/captcha.py:45
  /builds/kevr/aurweb/aurweb/captcha.py:45: DeprecationWarning: 'contextfilter' is renamed to 'pass_context', the old name will be removed in Jinja 3.1.
    def captcha_salt_filter(context):
aurweb/captcha.py:52
  /builds/kevr/aurweb/aurweb/captcha.py:52: DeprecationWarning: 'contextfilter' is renamed to 'pass_context', the old name will be removed in Jinja 3.1.
    def captcha_cmdline_filter(context, salt):
aurweb/l10n.py:92
  /builds/kevr/aurweb/aurweb/l10n.py:92: DeprecationWarning: 'contextfilter' is renamed to 'pass_context', the old name will be removed in Jinja 3.1.
    def tr(context: typing.Any, value: str):
-- Docs: https://docs.pytest.org/en/stable/warnings.html
======================= 134 passed, 4 warnings in 58.68s =======================

This warning specifically talks about the decorator we use to create context-aware filters, like tr. We need to replace all instances of @contextfilter with @pass_context, as far as I can tell.