update CHANGELOG

Author: stephprince

CHANGELOG.md

@@ -2,9 +2,13 @@
 
 ## PyNWB 3.1.3 (Unreleased)
 
+### Fixed
+- Fixed incorrect warning for path not ending in `.nwb` when no path argument was provided. @t-b [#2130](https://github.com/NeurodataWithoutBorders/pynwb/pull/2130)
+
 ### Documentation and tutorial enhancements
 - Change UI of assistant to be an accordion that is always visible. [#2124](https://github.com/NeurodataWithoutBorders/pynwb/pull/2124)
 
+
 ## PyNWB 3.1.2 (August 13, 2025)
 
 ### Fixed