enable the type-repr simplification unconditionally in the stack trace

Since keyword pairs can appear within positional arguments, it can be
confusing if we print the same type with different representations.

base/show.jl

@@ -1117,11 +1117,11 @@ function show_datatype(io::IO, x::DataType, wheres::Vector{TypeVar}=TypeVar[])
             print(io, "}")
             return
         end
-    elseif get(io, :simplify_kwstype, false)::Bool && kwsnt !== nothing
+    elseif get(io, :backtrace, false)::Bool && kwsnt !== nothing
         # simplify the type representation of keyword arguments
-        # when printing signature of keyword method
+        # when printing signature of keyword method in the stack trace
         print(io, "@Kwargs{")
-        show_at_namedtuple(io, kwsnt.parameters...)
+        show_at_namedtuple(io, kwsnt.parameters[1]::Tuple, kwsnt.parameters[2]::DataType)
         print(io, "}")
         return
     end

base/stacktraces.jl

@@ -352,7 +352,6 @@ function show_spec_sig(io::IO, m::Method, @nospecialize(sig::Type))
                 kwnames[i] = Symbol(str[1:end-3])
             end
         end
-        io = IOContext(io, :simplify_kwstype=>true) # see the comment in `show_datatype`
         Base.show_tuple_as_call(io, m.name, pos_sig;
                                 demangle=true,
                                 kwargs=zip(kwnames, kwarg_types),