Remove --recursive from instructions

[makoncline]

I was getting the error Unknown options: --recursive when running lines 67 and 68 of the readme with aws-cli/2.1.15.
When the --recursive option is removed, the command works.

Issue #, if available:

Description of changes:

Checklist

• 👋 I have run the unit tests, and all unit tests have passed.
• ⚠️ This pull request might incur a breaking change.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[beomseoklee]

@makoncline Thanks for your feedback. We'll update README.md in the next release.

[8secz-johndpope]

yes - I had to skip this step. Otherwise smooth.
There's no mention of crafting the url eg
/200x200/image.jpg

I came here from another repo - I was sure it did it - now I can't find the instructions anywhere.

sagidM/s3-resizer#21

Let's say we have some shared image in S3, for example:
https://example.com/images/pretty_photo.jpg

to resize on fly this image to, say, 150x150, we can make a request like this:
https://example.com/images/150x150/pretty_photo.jpg

[G-Lenz]

We have updated README.md in v5.2.0.

[beomseoklee]

Thanks for your contribution, and this was added in the current version.
Because of our internal policy, we couldn't merge the PR directly so we put your name as a contributor in https://github.com/aws-solutions/serverless-image-handler#external-contributors.

Once again, thanks for your contribution.