Fix location of a changelog item

The panic handler change accidentally went under the previous release's
section. Move it up to the current unreleased version.

Author: nicholasbishop

CHANGELOG.md

@@ -45,6 +45,12 @@
 
 ## uefi-services - [Unreleased]
 
+### Changed
+
+- Changed the panic handler log message to use `println!` instead of
+  `error!`. This removes an extraneous file name and line number from
+  the log message.
+
 ## uefi - 0.17.0
 
 ### Added
@@ -118,10 +124,6 @@
 
 - The `no_panic_handler` feature has been replaced with an additive
   `panic_handler` feature. The new feature is enabled by default.
-- Changed the panic handler log message to use `println!` instead of
-  `error!`. This removes an extraneous file name and line number from
-  the log message.
-
 ## uefi - 0.16.1
 
 ### Added