Icon: Fix React warning for `svgPath={undefined}`

Created by: umpox

Description

Previous code meant that it was possible to pass the svgPath prop down as a DOM attribute.

Test plan

Tested locally at https://sourcegraph.test:3443/users/jeff.wayman/batch-changes/deploy-docs-folder-links-rename/executions/QmF0Y2hTcGVjOiI2WEtUUnRSd0Z3eSI=/execution/workspaces/QmF0Y2hTcGVjV29ya3NwYWNlOjk5MjAyMw==?visible=15

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.