add tables.getOrDefault param name change to changelog (#24271)

refs
https://github.com/nim-lang/Nim/issues/23587#issuecomment-2404406187

changelog.md

@@ -8,6 +8,10 @@ floating point numbers that are minimal in size and possess round-trip and corre
 rounding guarantees (via the
 [Dragonbox](https://raw.githubusercontent.com/jk-jeon/dragonbox/master/other_files/Dragonbox.pdf) algorithm). Use `-d:nimLegacySprintf` to emulate old behaviors.
 
+- The `default` parameter of `tables.getOrDefault` has been renamed to `def` to
+  avoid conflicts with `system.default`, so named argument usage for this
+  parameter like `getOrDefault(..., default = ...)` will have to be changed.
+
 ## Standard library additions and changes
 
 [//]: # "Changes:"