[fix] Dump map expressions with current syntax

Map expressions use currentt map constructor syntax.
`map { $key : $value }`

Author: line-o

exist-core/src/main/java/org/exist/xquery/functions/map/MapExpr.java

@@ -118,7 +118,7 @@ public void dump(final ExpressionDumper dumper) {
         dumper.display("map {");
         for (final Mapping mapping : this.mappings) {
             mapping.key.dump(dumper);
-            dumper.display(" := ");
+            dumper.display(" : ");
             mapping.value.dump(dumper);
         }
         dumper.display("}");