SQL: [Docs] Fix example for DATETIME_PARSE (#56409)

When no timezone is specified the session timezone is used without
conversion, fix the docs test accordingly.

Follows: #56158

Author: matriv

x-pack/plugin/sql/qa/src/main/resources/docs/docs.csv-spec

@@ -2778,8 +2778,8 @@ schema::datetime:ts
 }
 
       datetime
-------------------------------------
-2020-04-07T08:20:30.000Europe/Athens
+-----------------------------
+2020-04-07T10:20:30.000+03:00
 // end::dateTimeParse3
 ;