Add changelog entry: Sparkline can have any height

Author: uriyyo

CHANGELOG.md

@@ -12,7 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added `GridLayout.max_column_width` https://github.com/Textualize/textual/pull/6228
 - Added `Content.fold` https://github.com/Textualize/textual/pull/6238
 - Added `strip_control_codes` to Content constructors https://github.com/Textualize/textual/pull/6238
-
+- Allow `Sparkline` to be of any height, not just 1 https://github.com/Textualize/textual/pull/6171
 
 ### Changed