Redundant of removed.

Author: Karsten7

source/reference/operator/aggregation/toLong.txt

@@ -21,7 +21,7 @@ Definition
 
    .. versionadded:: 4.0
 
-   Converts a value of to a long. If the value cannot be converted
+   Converts a value to a long. If the value cannot be converted
    to a long, :expression:`$toLong` errors. If the value is null or
    missing, :expression:`$toLong` returns null.