fix invalidations related to ismutable (#52170)

Related to #52134. It would be nice if the underlying inference issue
was fixed but this seems to be a hotfix for now.

I have seen this inference problem occurring in Julia v1.9, v1.10, and
current `master`. For example, on Julia v1.9.3, I get

```julia

julia> code_warntype(ismutable, (Function,))
MethodInstance for ismutable(::Function)
  from ismutable(x) @ Base reflection.jl:521
Arguments
  #self#::Core.Const(ismutable)
  x::Function
Body::Any
1 ─      nothing
│        nothing
│   %3 = Base.typeof(x)::Type{<:Function}
│   %4 = Base.getproperty(%3, :name)::Any
│   %5 = Base.getproperty(%4, :flags)::Any
│   %6 = (%5 & 0x02)::Any
│   %7 = (%6 == 0x02)::Any
└──      return %7
```

This causes some invalidations when `using OrdinaryDiffEq`.

base/reflection.jl

@@ -627,7 +627,9 @@ true
 !!! compat "Julia 1.5"
  This function requires at least Julia 1.5.
 """
-ismutable(@nospecialize(x)) = (@_total_meta; typeof(x).name.flags & 0x2 == 0x2)
+ismutable(@nospecialize(x)) = (@_total_meta; (typeof(x).name::Core.TypeName).flags & 0x2 == 0x2)
+# The type assertion above is required to fix some invalidations.
+# See also https://github.com/JuliaLang/julia/issues/52134
 
 """
  ismutabletype(T) -> Bool