Fix intermittent failure in test_known_telescopes

[kartographer]

Description

Fixes an issue w/ test_known_telescopes, where some downloading issues appear to have caused a race condition (causing some CIs to fail).

Motivation and Context

Trying to avoid CI jobs failing b/c of flaky tests....

(also, apparently if you tell an AI agent to draft a PR, it'll just generate and push the whole thing without asking, oy!)

Types of changes

• Build or continuous integration change

Checklist:

• I have read the contribution guide.
• My code follows the code style of this project.

Build or continuous integration change checklist:

• If required or optional dependencies have changed (including version numbers), I have updated the readme, pyproject.toml, environment.yaml and CI conda yaml files to reflect the changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.93%. Comparing base (18f4f6a) to head (6e632cf).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1697   +/-   ##
=======================================
  Coverage   99.93%   99.93%           
=======================================
  Files          67       67           
  Lines       22982    22982           
=======================================
  Hits        22968    22968           
  Misses         14       14           

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[bhazelton]

Looks reasonable. It's possible this is now happening because of a change I made in #1685 -- now on newer versions of astropy we shouldn't need to refresh the cache every time. If we continue to have trouble we can revisit that change...