Add tracking issue number

Author: nxsaken

library/core/src/mem/manually_drop.rs

@@ -217,7 +217,7 @@ impl<T> ManuallyDrop<T> {
     ///
     #[must_use = "if you don't need the value, you can use `ManuallyDrop::drop` instead"]
     #[stable(feature = "manually_drop_take", since = "1.42.0")]
-    #[rustc_const_unstable(feature = "const_manually_drop_take", issue = "none")]
+    #[rustc_const_unstable(feature = "const_manually_drop_take", issue = "148773")]
     #[inline]
     pub const unsafe fn take(slot: &mut ManuallyDrop<T>) -> T {
         // SAFETY: we are reading from a reference, which is guaranteed