fix: update vendored Font Awesome webfonts to match the 6.7.2 CSS

The files under static/assets/webfonts dated from April 2024 while the
stylesheet is compiled from @fortawesome/fontawesome-free 6.7.2. The
stale fa-solid-900.woff2 carried invalid glyph bounding boxes, which
Firefox's font sanitizer reports on every page load ('Glyph bbox was
incorrect; adjusting'), and a version gap between font and CSS risks
wrong/missing icons for newly mapped codepoints. Re-vendored all eight
font files from the installed 6.7.2 package (0 incorrect bboxes).

Author: duruer