Merge pull request #3251 from bdarnell/release-6.3

Set version to 6.3 final

Author: bdarnell

docs/releases/v6.3.0.rst

@@ -1,8 +1,8 @@
 What's new in Tornado 6.3.0
 ===========================
 
-In progress
------------
+Apr 17, 2023
+------------
 
 Highlights
 ~~~~~~~~~~

tornado/__init__.py

@@ -22,8 +22,8 @@
 # is zero for an official release, positive for a development branch,
 # or negative for a release candidate or beta (after the base version
 # number has been incremented)
-version = "6.3b1"
-version_info = (6, 3, 0, -99)
+version = "6.3"
+version_info = (6, 3, 0, 0)
 
 import importlib
 import typing