Redundant of removed.

Author: Karsten7

source/reference/operator/aggregation/toDecimal.txt

@@ -22,7 +22,7 @@ Definition
 
    .. versionadded:: 4.0
 
-   Converts a value of to a decimal. If the value cannot be converted
+   Converts a value to a decimal. If the value cannot be converted
    to a decimal, :expression:`$toDecimal` errors. If the value is null or
    missing, :expression:`$toDecimal` returns null.