New category name input appearance doesn't match other inputs

[johnbillion]

Description

When selecting the categories for a post, clicking the Add New Category button toggles the New Category Name text input. The appearance of this input does not match other text inputs in the sidebar. Its border is not the correct colour and its border radius is too great.

Step-by-step reproduction instructions

1. Create or edit a post
2. Open the Categories panel in the Post sidebar
3. Click the Add New Category button
4. Compare the visual style of the New Category Name text input with others, for example the URL Slug and the Add New Tag inputs
5. Observe that the border style and colour don't match

Screenshot

WordPress information

• WordPress version: 5.6
• Gutenberg version: WordPress core block editor
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? Yes, Twenty Twenty-One

Device information

• Device: Desktop
• Operating system: macOS
• Browser: Chrome 88