USWDS-Site - migrationV3: removes type="button" from button migration code

[Sgtpluck]

Summary

Removed type that overwrote type="search" for search button migration

Problem statement

Copy/pasting the updated search button code does not work because type="search" was left in from the old code.

Solution

Removes type="button" from the new code

Before opening this PR, make sure you’ve done whichever of these applies to you:

• [ ] Confirm that this code follows the 18F Front End Coding Style Guide and Accessibility Guide.
• [ ] Run git pull origin [base branch] to pull in the most recent updates from your base and check for merge conflicts. (Often, the base branch is main).
• [ ] Run npm run prettier:scss to format any Sass updates.
• [ ] Run npm test and confirm that all tests pass.
• [ ] Run your code through HTML_CodeSniffer and make sure it’s error free.