Auto merge of #82338 - RalfJung:interp-error-allocs, r=oli-obk

all InterpError allocate now, so adjust alloc-error-check

Cc https://github.com/rust-lang/rust/pull/82116#discussion_r578310770
r? `@oli-obk`

compiler/rustc_mir/src/transform/const_prop.rs

@@ -466,8 +466,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 // an allocation, which we should avoid. When that happens,
                 // dedicated error variants should be introduced instead.
                 assert!(
-                    !error.kind().allocates(),
-                    "const-prop encountered allocating error: {}",
+                    !error.kind().formatted_string(),
+                    "const-prop encountered formatting error: {}",
                     error
                 );
                 None