Update smol_str to 0.3.1

[bushrat011899]

• Tested on all platforms changed
  • Tested on my own machine (Windows 10 Intel x64)
  • Have not tested on other platforms, but am not expecting issues as smol_str 0.2 to 0.3 was a relatively minor set of changes.
• Added an entry to the changelog module if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

Objective

Update smol_str to 0.3.1, allowing other projects to update as well.

Solution

Updated smol_str to 0.3.1 with no other changes required.

Motivation

Bevy would like to update to the latest version but is blocked due to winit

[kchibisov]

Bevy would like to update to the latest version but is bevyengine/bevy#15113 due to winit

Unless bevy follows git master, it won't do anything for them, because it's a breaking change, since smol_str is a part of the public API.

[bushrat011899]

Yeah that makes sense. I'm not familiar with the release cycle for winit but I imagine this would be merged in for a 0.31 release.