Add changelog entry to Modal focus trap guidance.

Replacing this:

Test print outputs. Test printing using a variety of printers, print-to-PDF options, and assistive output devices, using representative browser and operating system combinations prior to launch. Remember that mobile device users will have additional challenges printing or saving to PDF so some on-screen guidance may be necessary.

with this:
Test print outputs. Test printing using a variety of printers, print-to-PDF options, and assistive output devices, using representative browser and operating system combinations based on your site's visitor data prior to launch. Remember that mobile device users will have additional challenges printing or saving to PDF so some on-screen guidance may be necessary.

Will need updated date when ready to publish

…eprecord_update

Updating content and link in Test broadly section

USWDS-Site - Modal: Update accessibility guidance

USWDS-site: Replace nunjucks reference

…angelog-6026