chore(deps): update dependency boto3 to v1.12.16 (#3054)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [boto3](https://togithub.com/boto/boto3) | patch | `==1.12.15` -> `==1.12.16` |

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### Release Notes

<details>
<summary>boto/boto3</summary>

### [`v1.12.16`](https://togithub.com/boto/boto3/blob/master/CHANGELOG.rst#&#8203;11216)

[Compare Source](https://togithub.com/boto/boto3/compare/1.12.15...1.12.16)

=======

-   api-change:`signer`: [``botocore``] Update signer client to latest version
-   api-change:`guardduty`: [``botocore``] Update guardduty client to latest version
-   api-change:`appmesh`: [``botocore``] Update appmesh client to latest version
-   api-change:`ec2`: [``botocore``] Update ec2 client to latest version
-   api-change:`robomaker`: [``botocore``] Update robomaker client to latest version

</details>

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storage/s3-sdk/requirements.txt

@@ -1 +1 @@
-boto3==1.12.15
+boto3==1.12.16