Is_integer function documentation needs update

[hkaushal]

As per the is_integer function's documentation, the function can expect a Column or A super. We ran into issue while we passed it a Varchar type field. Here is the code we ran

CREATE TEMP TABLE t(s char(100));
INSERT INTO t VALUES ('5');
SELECT s, is_integer(s) FROM t;

[joshbean]

Closing this issue or pull request in advance of archiving this repo. For more information about the decision to archive this repo (and others in the 'awsdocs' org), see the announcement on the AWS News Blog.