Update CHANGELOG.md

Author: Zeroto521

CHANGELOG.md

@@ -18,6 +18,7 @@
 ### Fixed
 - Raised an error when an expression is used when a variable is required
 - Fixed some compile warnings
+- Fixed the type of @ matrix operation result from MatrixVariable to MatrixExpr.
 ### Changed
 - MatrixExpr.sum() now supports axis arguments and can return either a scalar or MatrixExpr, depending on the result dimensions.
 - AddMatrixCons() also accepts ExprCons.