Remove references to DALL·E image models

[dkotter]

What?

Removes any references to OpenAI's DALL·E image models

Why?

OpenAI announced that the DALL·E image models (both 2 and 3) are being deprecated on May 12. I had thought we were still referencing DALL·E 3 in our preferred image model list but apparently I had already removed that in #361. We still had a few references in documentation and tests so this PR removes those.

How?

• Removes any references to DALL·E image models in our documentation
• Removes the DALL·E image models from our mock test response

Use of AI Tools

None

Testing Instructions

None needed. Ensure tests pass

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.75%. Comparing base (cf3f12a) to head (23ec8a0).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #414   +/-   ##
==========================================
  Coverage      65.75%   65.75%           
  Complexity       763      763           
==========================================
  Files             53       53           
  Lines           3863     3863           
==========================================
  Hits            2540     2540           
  Misses          1323     1323           

Flag	Coverage Δ
unit	65.75% <ø> (ø)

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