[FFI] Remove backwards-compatibility unwrapping of IntImm

This is a follow-up PR to apache#16183,
which updated the FFI with explicit integer types.  As part of that
change, many internal functions were updated to accept non-IR
types (e.g. `Array<runtime::Int>` instead of `Array<IntImm>`).  For
backwards compatibility with callees that provided the IR types, a
specialization of `PackedFuncValueConverter` unwrapped the `IntImm`
into a `runtime::Int`.

This commit removes the backwards-compatibility specialization of
`PackedFuncValueConverter`.  Breakages that are found in CI as a
result will then be updated at the caller side, removing the need for
the backwards-compatibility handler altogether.

include/tvm/ir/expr.h

@@ -866,28 +866,6 @@ struct PackedFuncValueConverter<tvm::FloatImm> {
   }
 };
 
-/* \brief Backwards compatibility wrapper for IntImm arguments
- *
- * In previous versions of TVM, IntImm was the default FFI type for
- * integer arguments, instead of runtime::Int.  For backwards
- * compatibility where the callee has been updated to expected a
- * runtime::Int, the caller has not been updated to provide a
- * runtime::Int (e.g. relay script parsing), and the auto-unboxing of
- * runtime::Int does not apply (e.g. making an `Array<runtime::Int>`),
- * allow the IntImm to be generated.
- */
-template <>
-struct PackedFuncValueConverter<runtime::Int> {
-  template <typename PODSubclass>
-  static runtime::Int From(const PODSubclass& val) {
-    if (val.template IsObjectRef<tvm::IntImm>()) {
-      return runtime::Int(val.template AsObjectRef<tvm::IntImm>()->value);
-    } else {
-      return val.template AsObjectRef<runtime::Int>();
-    }
-  }
-};
-
 }  // namespace runtime
 }  // namespace tvm