Dict comprehensions are not tested at all in `test_named_expressions.py`

[sobolevn]

While working on #100581 I've noticed that we do not test dict comprehensions at all there.

I think that this needs to be improved.
I will add test case for them soon, PR is in the works.

Linked PRs

• gh-100746: Improve test_named_expressions.py #116713
• [3.12] gh-100746: Improve test_named_expressions.py (GH-116713) #116747
• [3.11] gh-100746: Improve test_named_expressions.py (GH-116713) #116748