Issues on the user defined functions query

The following example is not working properly which is at https://age.apache.org/age-manual/master/functions/user_functions.html
It has multiple issues:
1. Missing ')' closing parentheses
2. Missing typecasting
3. Result is incorrect (sqrt(25) is 5 while the result is mentioned as 25)

Test environment:

PG: 11
AGE: 1.2.0
OS: Ubuntu 18

**The output after having getting the closing parentheses fixed:**

```SQL
rrr=# SELECT *
rrr-# FROM cypher('test', $$
rrr$# RETURN pg_catalog.sqrt(25)
rrr$# $$) as (result agtype);
ERROR: function pg_catalog.sqrt(agtype) does not exist
LINE 3: RETURN pg_catalog.sqrt(25)
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
```