Update release notes

Author: timoast

NEWS.md

@@ -6,6 +6,7 @@ New features:
 
 Other changes:
 
+* Enable using a 6-column fragment file ([#1945](https://github.com/stuart-lab/signac/issues/1945))
 * Improve error messages for `FindMotifs()` ([#1788](https://github.com/stuart-lab/signac/issues/1788))
 * Add documentation about the required format for gene annotations, and ensure this format is present when creating the assay ([#1797](https://github.com/stuart-lab/signac/pull/1797); [@lldelisle](https://github.com/lldelisle))
 * Fix error in `RegionPlot()` x-axis ([@cmf1997](https://github.com/cmf1997); [#1899](https://github.com/stuart-lab/signac/pull/1899))