stabilize min_const_unsafe_fn -- revert const-size_of-cycle changes

Author: Centril

src/test/ui/consts/const-size_of-cycle.stderr

@@ -5,6 +5,10 @@ LL |     bytes: [u8; std::mem::size_of::<Foo>()]
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: ...which requires const-evaluating `Foo::bytes::{{constant}}`...
+  --> $SRC_DIR/libcore/mem.rs:LL:COL
+   |
+LL |     intrinsics::size_of::<T>()
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 note: ...which requires computing layout of `Foo`...
 note: ...which requires normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All }, value: [u8; _] }`...
 note: ...which requires const-evaluating + checking `Foo::bytes::{{constant}}`...