Update NEWS.md

Co-Authored-By: Lyndon White <[email protected]>

NEWS.md

@@ -32,7 +32,7 @@ Standard library changes
 
 * The methods of `mktemp` and `mktempdir` which take a function body to pass temporary paths to no longer throw errors if the path is already deleted when the function body returns ([#33091]).
 
-* New function `only(x)` returns the one-and-only element of a collection `x`, and throws an error if `x` contains zero or multiple elements.
+* New function `only(x)` returns the one-and-only element of a collection `x`, and throws an error if `x` contains zero or multiple elements. [#33129]
 
 #### Libdl