Simplify calls to tcx.mk_const

`mk_const(ty::ConstKind::X(...), ty)` can now be simplified to
`mk_cosnt(...,                   ty)`.

I searched with the following regex: \mk_const\([\n\s]*(ty::)?ConstKind\
I've left `ty::ConstKind::{Bound, Error}` as-is, they seem clearer this
way.

compiler/rustc_middle/src/mir/mod.rs

@@ -2527,8 +2527,7 @@ impl<'tcx> ConstantKind<'tcx> {
                 let generics = tcx.generics_of(item_def_id);
                 let index = generics.param_def_id_to_index[&def_id];
                 let name = tcx.item_name(def_id);
-                let ty_const =
-                    tcx.mk_const(ty::ConstKind::Param(ty::ParamConst::new(index, name)), ty);
+                let ty_const = tcx.mk_const(ty::ParamConst::new(index, name), ty);
                 debug!(?ty_const);
 
                 return Self::Ty(ty_const);