Fix a typo in IAM Policy section description

[ehudon]

Context

I am currently working with the S3 plugin and noticed a typo in the description of the IAM policy section. I thought I would fix it while I am at it.

Nature of change

In the example we can see:

arn:aws:s3:::my-s3bucket/*

This won't match my-s3bucket-test but rather my-s3bucket/test.