[Docs] Update SQL examples in documentation for timestamp/datetime functions

[codetyri0n]

PRs - #19078 and #18990
bring in support for setting config options for timezone with SET datafusion.execution.time_zone statement.

TO DO : Update the documentation's corresponding SQL examples for the above functions (once above PRs are merged) like in #18200

[codetyri0n]

CC : @Omega359