fix(a11y): Spread `rest` props to DropdownToggle button component

Created by: plibither8

This PR spreads all supplied props sent to RepoHeaderActionDropdownToggle component, to the Button component, thereby sending attributes like aria-label too.

Closes #35852 (closed)

Test plan

• Tested using a screen reader
• Checked via Dev Tools that the aria-label="Repository Actions" attribute is now present on the toggle button.

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.