`types.UnionType` + `Literal` types are not tested together

[sobolevn]

Literal had some known problems when used with typing.Union and types.UnionType.
Example: #103592

I've covered typing.Union, see #103706
But, I forgot about types.UnionType.

So, I will add this new test as a part of this issue.

Linked PRs

• gh-103746: Test types.UnionType and Literal types together #103747
• [3.11] gh-103746: Test types.UnionType and Literal types together (GH-103747) #103772