doc: release: 4.3: finalize release notes and migration guide

Remove working draft status from the 4.3.0 release notes and migration
guide.

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

doc/releases/migration-guide-4.3.rst

@@ -7,8 +7,8 @@
 
 .. _migration_4.3:
 
-Migration guide to Zephyr v4.3.0 (Working Draft)
-################################################
+Migration guide to Zephyr v4.3.0
+################################
 
 This document describes the changes required when migrating your application from Zephyr v4.2.0 to
 Zephyr v4.3.0.

doc/releases/release-notes-4.3.rst

@@ -26,8 +26,8 @@
 
 .. _zephyr_4.3:
 
-Zephyr 4.3.0 (Working Draft)
-############################
+Zephyr 4.3.0
+############
 
 We are pleased to announce the release of Zephyr version 4.3.0.