[typescript] Remove key prop from Snackbar

[TorstenStueber]

The prop key should not be part of the Snackbar props for the following reasons:

• key is a special prop that is automatically declared for every React component
• key is defined to be string | number | null in general (not number as was here – way too restrictive)

[TorstenStueber]

Sorry for bothering you with this trivial PR. It is annoying, though, as the standard use case for Snackbar key would be to use the message itself (i.e., a string).

This use case is even suggested in the comment in Snackbar.js. But maybe one should even remove the prop key in Snackbar.js as well (in accordance with the TypeScript type). I just kept it there because I found the comment (mentioned above) useful.

[sebald]

PRs like that are never bothering! What ever the opposite of bothering is, you're doing it! Thanks a lot for taking the time! 🙌