Remove NatLit desugaring error variant

lang/lowering/src/result.rs

@@ -65,12 +65,6 @@ pub enum LoweringError {
         #[label]
         span: SourceSpan,
     },
-    #[error("Literal cannot be desugared because S/Z are not in program")]
-    #[diagnostic(code("L-010"))]
-    NatLiteralCannotBeDesugared {
-        #[label]
-        span: SourceSpan,
-    },
     #[error("Mismatched named arguments: given {}, expected {}", given.id, expected.id)]
     #[diagnostic(code("L-011"))]
     MismatchedNamedArgs {

test/suites/fail-lower/L-010.expected

@@ -1,8 +0,0 @@
-L-010
-
-  × Literal cannot be desugared because S/Z are not in program
-   ╭─[L-010.pol:3:17]
- 2 │ 
- 3 │ let foo : Nat { 5 }
-   ·                 ─
-   ╰────

test/suites/fail-lower/L-010.pol

@@ -1,3 +0,0 @@
-data Nat {}
-
-let foo : Nat { 5 }