Updated tracking issue for String::splice and its unstable-book entry

Author: budziq

src/doc/unstable-book/src/library-features/splice.md

@@ -1,14 +1,13 @@
 # `splice`
 
-The tracking issue for this feature is: [#32310]
+The tracking issue for this feature is: [#44643]
 
-[#32310]: https://github.com/rust-lang/rust/issues/32310
+[#44643]: https://github.com/rust-lang/rust/issues/44643
 
 ------------------------
 
 The `splice()` method on `String` allows you to replace a range
-of values in a string with another range of values, and returns
-the replaced values.
+of values in a string with another range of values.
 
 A simple example:
 

src/liballoc/string.rs

@@ -1451,7 +1451,7 @@ impl String {
     /// s.splice(..beta_offset, "Α is capital alpha; ");
     /// assert_eq!(s, "Α is capital alpha; β is beta");
     /// ```
-    #[unstable(feature = "splice", reason = "recently added", issue = "32310")]
+    #[unstable(feature = "splice", reason = "recently added", issue = "44643")]
     pub fn splice<R>(&mut self, range: R, replace_with: &str)
         where R: RangeArgument<usize>
     {