Remove Field Sizing Workaround in Spright Chat Input

[hellovolcano]

🧹 Tech Debt

The Spright Chat Input control is used in an application with an embedded browser that does not yet support the field-sizing CSS property. Once that application upgrades the browser, we should remove the JS workaround added to that control.

(I will add a link to the work item tracking that upgrade shortly).

[jattasNI]

I guess we should also wait for Firefox to support field-sizing:

https://caniuse.com/?search=field-sizing
https://bugzilla.mozilla.org/show_bug.cgi?id=1832409
https://bugzilla.mozilla.org/show_bug.cgi?id=1977177