Typst 0.13 compatibility: Fix 1 more error and 2 warnings

[eltos]

• Fix another error "Cannot add type and string"
• Fix two warning "Unnecessary import rename to same name"

For #52

[tingerrr]

LGTM

[tingerrr]

Thank you!

[QuadnucYard]

Hello! When I searched the codebase, I found more cases add string and type not fixed.

valkyrie/src/types/logical.typ

Line 43 in 8b47671

) + ". Got " + type(it)

valkyrie/src/coercions.typ

Line 107 in 8b47671

panic("Unknown date of type '" + type(it) + "' accepts: datetime, str, int, and object")

[tingerrr]

PR would be appreciated, I'd prepare another patch release in that case.