Update Tor to 0.4.4.6

[emkll]

Status

Ready for review

Description of Changes

Towards #5624 .
Closes #5649 ?

Testing

• Updated tor signing key is valid, only subkey was updated
• make fetch-tor-debs is working as expected, for both xenial and focal

Deployment

These packages will be deployed once the deb packages are uploaded apt.freedom.press.

Checklist

If you made changes to the server application code:

• Linting (make lint) and tests (make test) pass in the development container

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

Choose one of the following:

• I have opened a PR in the docs repo for these changes, or will do so later
• I would appreciate help with the documentation
• These changes do not require documentation

[zenmonkeykstop]

Version and key are updated.

• updated subkey checks out.
• make fetch-tor-packages behaves as expected
• checksums match those in the corresponding PR: Update tor to 0.4.4.6 securedrop-apt-test#76

Looks good, ship it (once flaky CI passes).