Standardize changelog name in docs, point to it

Author: adamchainz

HISTORY.rst

@@ -1 +1 @@
-See https://github.com/adamchainz/django-mysql/blob/main/CHANGELOG.rst
+See https://django-mysql.readthedocs.io/en/latest/changelog.html

CHANGELOG.rst renamed to docs/changelog.rst

@@ -31,7 +31,7 @@ action, or get started with :doc:`installation`. Otherwise, take your pick:
    test_utilities
    exceptions
    contributing
-   history
+   changelog
 
 Indices and tables
 ==================

docs/history.rst

@@ -36,7 +36,7 @@ keywords =
     MariaDB
 project_urls =
     Documentation = https://django-mysql.readthedocs.io/
-    Changelog = https://github.com/adamchainz/django-mysql/blob/main/CHANGELOG.rst
+    Changelog = https://django-mysql.readthedocs.io/en/latest/changelog.html
     Mastodon = https://fosstodon.org/@adamchainz
     Twitter = https://twitter.com/adamchainz