Also downgrade vinyl-fs to v3.0 to fix stream error handling (#10135)

The vinyl-fs package was upgraded from v3.0 to v4.0 at the same time
as gulp-imagemin (commit 226f6cc). This major version bump changed
how vinyl-fs handles stream errors.

With vinyl-fs v4, when the optional imagemin plugins (gifsicle,
jpegtran, optipng) fail to load or compile, the build stream fails
completely without creating output files, resulting in:
  Error: ENOENT: no such file or directory, scandir 'ui/public/_'

vinyl-fs v3.0 handled these optional dependency failures gracefully
and allowed the build to continue even when optimization plugins
weren't available.

This is why the build worked before both dependencies were upgraded.

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: rosieyohannan