Revert "[mlir] Silence a few -Wunused-but-set-parameter warnings" (#68667)

A cmake patch append compile options `-Wno-unused-but-set-parameter` is
merged.

This reverts commit 82ae83a.

Author: lipracer

mlir/include/mlir/IR/Attributes.h

@@ -409,7 +409,6 @@ struct CastInfo<To, From,
     /// Return a constant true instead of a dynamic true when casting to self or
     /// up the hierarchy.
     if constexpr (std::is_base_of_v<To, From>) {
-      (void)ty;
       return true;
     } else {
       return To::classof(ty);

mlir/include/mlir/IR/Types.h

@@ -406,7 +406,6 @@ struct CastInfo<
     /// Return a constant true instead of a dynamic true when casting to self or
     /// up the hierarchy.
     if constexpr (std::is_base_of_v<To, From>) {
-      (void)ty;
       return true;
     } else {
       return To::classof(ty);

mlir/include/mlir/IR/Value.h

@@ -605,7 +605,6 @@ struct CastInfo<
     /// Return a constant true instead of a dynamic true when casting to self or
     /// up the hierarchy.
     if constexpr (std::is_base_of_v<To, From>) {
-      (void)ty;
       return true;
     } else {
       return To::classof(ty);