[fix] small search variant button has no accessible name

[shkeating]

ReactUSWDS Version 6.2.0 USWDS Version: 3.7.1

Describe the bug
The small search variant with a magnifying glass as a button do not have an accessible name. the impact is that users on assistive tech will not receive sufficient context about what the button does.

To Reproduce
Steps to reproduce the behavior:

1. Go to Search: Small Variant, React USWDS Storybook
2. Open the canvas in a new tab
3. Open ANDI
4. See warning message about lack of accessible name on the button

Expected behavior
In the USWDS documentation and examples, the button has a label of Search provided via alt text on the img tag contained in the button

If we add alt text to the svg in our version, this should remediate the issue.

Screenshots

Additional context
Accessibility guidance on USWDS website