Jetpack: font format warning in Firefox

**Steps to reproduce:**

- Use Firefox (I tested with v95.0.2 on macOS). Have the dev console open with warnings displayed.
- On a WordPress site with the Jetpack plugin activated, navigate to the wp-admin dashboard.
- Observe the following warning:

> downloadable font: no supported format found (font-family: "jetpack" style:normal weight:400 stretch:100 src index:1) source: (end of source list)

**Thoughts:**

The Jetpack icon in the menu bar is sourced via [this file](https://github.com/Automattic/jetpack/blob/master/projects/plugins/jetpack/scss/jetpack-icons.scss).

Two things aren't clear to me:

1. What this media query is intended to do (that the preceding `@font-face` block won't do):

https://github.com/Automattic/jetpack/blob/87bc46bdb80a1223a58b1cab4eee9bc2668d2380/projects/plugins/jetpack/scss/jetpack-icons.scss#L16-L21

If the media query block is commented out, and Jetpack rebuilt, the warning will go away.

2. The `jetpack.svg#jetpack` src seems not to be working 🤷 If you manually edit sources to just the svg for testing, it doesn't seem to load which I suspect it should, but I'm not too familiar with fonts/svg.

Internal, reported via: p8oabR-LV-p2#comment-5715

Start with projects/plugins/jetpack/scss/jetpack-icons.scss and reproduce the Firefox warning on a WordPress admin dashboard with the Jetpack plugin activated. Inspect the media-query @font-face block and the jetpack.svg#jetpack source, then rebuild Jetpack to verify the warning is gone and the Jetpack icon still loads.

Written by the indexing model from the issue text.