New custom dialog boxes have a max width of 600px

[svkcode]

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Developer environment

Windows

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

Describe the bug / error

A recent update to dialog boxes (rounded corners) in SharePoint is causing dialogs created with the sp-dialog library to have a max width of 600px. Content that is larger than 600px that used to fit is now overflowing.

Steps to reproduce

1. Create a SPFx command set extension that displays a custom dialog box using the sp-dialog library with content larger than 600px
2. Run the extension on a SharePoint list and execute the command to display the custom dialog

Expected behavior

Custom dialog boxes should expand to fit their content