Update change log for attachment description escaping

[stevenmccullaghmadetech]

What

Updating changelog for the Pystash file attachment escaping issue previously merged.

Why

Code was merged in previously to verify a fix, but change log needs updated to reflect the same.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have updated the Changelog with details of my change in the UNRELEASED section if this change will affect end users

[adrianclay]

Because this is a potentially breaking change, I think we should be a bit more specific about what outbound request attributes are affected, and what escaping is being performed, and that if you were previously escaping those fields in a similar way, you shouldn't do that anymore.

It might feel over the top, but helps create a sense to users that we care.