[Clippy] Swap repeat_vec_with_capacity to use diagnostic item instead of path

Author: GnomedDev

alloc/src/vec/mod.rs

@@ -477,6 +477,7 @@ impl<T> Vec<T> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use]
+    #[cfg_attr(not(test), rustc_diagnostic_item = "vec_with_capacity")]
     pub fn with_capacity(capacity: usize) -> Self {
         Self::with_capacity_in(capacity, Global)
     }