fix: use ] for closing it

Change-Id: I60dbc6fcacd47afa70ee85d56cad5a2d42190ee5
Reviewed-on: https://codereview.kdab.com/c/knut/+/141906
Tested-by: Continuous Integration <build@kdab.com>
Reviewed-by: Nicolas Arnaud-Cormos <nicolas@kdab.com>

src/core/rangemark.cpp

@@ -140,7 +140,7 @@ QString RangeMark::text() const
 
 QString RangeMark::toString() const
 {
-    return QString("[%1, %2)").arg(start()).arg(end());
+    return QString("[%1, %2]").arg(start()).arg(end());
 }
 
 /*!