update for 8.4.0-beta2 release

Author: jmckenna

en/development/changelog/changelog-8-4.txt

@@ -7,6 +7,13 @@
 The summary of major changes for this release can be found in the `HISTORY.md <https://github.com/MapServer/MapServer/blob/branch-8-4/HISTORY.md>`__
 file from the source directory.
 
+.. _changelog-8-4-0-beta2:
+
+Changes from 8.4.0-beta1 to 8.4.0-beta2
+=======================================
+
+* Emit explicit error message when proj.db cannot be found ( `#7204 <https://github.com/mapserver/mapserver/issues/7204>`__ ) (Even Rouault) : `68576d0 <https://github.com/mapserver/mapserver/commit/68576d0571baee81c2efe955db432da7f283a949>`__
+
 .. _changelog-8-4-0-beta1:
 
 Changes from 8.2.2 to 8.4.0-beta1