Remove StableMIR ICE workaround (#4235)

Per conversation in rust-lang/rust#138025,
[another PR](rust-lang/rust#137502) resolved
this issue upstream.

Resolves #3919

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under the terms of the Apache 2.0 and MIT licenses.

Author: carolynzech

kani-compiler/src/kani_middle/reachability.rs

@@ -84,14 +84,6 @@ where
     crate_items
         .iter()
         .filter_map(|item| {
-            // avoid stable MIR panic
-            // https://github.com/model-checking/kani/issues/3919
-            if let Ok(instance) = Instance::try_from(*item) {
-                let int_def_id = rustc_internal::internal(tcx, instance.def.def_id());
-                if matches!(tcx.def_kind(int_def_id), rustc_hir::def::DefKind::GlobalAsm) {
-                    return None;
-                }
-            };
             // Only collect monomorphic items.
             matches!(item.kind(), ItemKind::Fn)
                 .then(|| {