Update union-types.md

[liang3zy22]

This should be an error, "A union type A | B has as values all values". So update it.

[liang3zy22]

Strange. I clicked "Edit this page on github" then create this PR. But the branch is lampepfl:language-reference-stable. I think it should be lampepfl:main.

[SethTisue]

The original wording is correct, and it is also more idiomatic than the suggested replacement.

If you find it reads poorly, perhaps we could take some other tack entirely. Maybe:

A union type A | B includes all values of both types.

[liang3zy22]

Thanks, @SethTisue .

The original wording is correct, and it is also more idiomatic than the suggested replacement.

If you find it reads poorly, perhaps we could take some other tack entirely.

To me(maybe other people), it does reads poorly.

A union type A | B includes all values of both types.

I will update the patch as you suggested.

[SethTisue]

Thank you!