Rollup merge of #106714 - Ezrashaw:remove-e0490, r=davidtwco

remove unreachable error code `E0490`

AFAIK, the untested and undocumented error code `E0490` is now unreachable, it was from the days of the original borrow checker.

cc ``@GuillaumeGomez`` #61137

compiler/rustc_infer/src/infer/mod.rs

@@ -410,9 +410,6 @@ pub enum SubregionOrigin<'tcx> {
     /// Creating a pointer `b` to contents of another reference
     Reborrow(Span),
 
-    /// Data with type `Ty<'tcx>` was borrowed
-    DataBorrowed(Ty<'tcx>, Span),
-
     /// (&'a &'b T) where a >= b
     ReferenceOutlivesReferent(Ty<'tcx>, Span),
 
@@ -1978,7 +1975,6 @@ impl<'tcx> SubregionOrigin<'tcx> {
             RelateParamBound(a, ..) => a,
             RelateRegionParamBound(a) => a,
             Reborrow(a) => a,
-            DataBorrowed(_, a) => a,
             ReferenceOutlivesReferent(_, a) => a,
             CompareImplItemObligation { span, .. } => span,
             AscribeUserTypeProvePredicate(span) => span,