Administration: Update Dashicons to the latest version.

This change introduces the following new icons to the Dashicon font:

- `.dashicons-admin-site-alt (f11d)`
- `.dashicons-admin-site-alt2 (f11e)`
- `.dashicons-admin-site-alt3 (f11f)`
- `.dashicons-buddicons-activity (f452)`
- `.dashicons-buddicons-bbpress-logo (f12b)`
- `.dashicons-buddicons-buddypress-logo (f448)`
- `.dashicons-buddicons-community (f453)`
- `.dashicons-buddicons-forums (f449)`
- `.dashicons-buddicons-friends (f454)`
- `.dashicons-buddicons-groups (f456)`
- `.dashicons-buddicons-pm (f457)`
- `.dashicons-buddicons-replies (f451)`
- `.dashicons-buddicons-topics (f450)`
- `.dashicons-buddicons-tracking (f455)`
- `.dashicons-businessperson (f12e)`
- `.dashicons-businesswoman (f12f)`
- `.dashicons-color-picker (f131)`
- `.dashicons-editor-ltr (f129)`
- `.dashicons-editor-ol-rtl (f12c)`
- `.dashicons-email-alt2 (f10a)`
- `.dashicons-instagram (f12d)`
- `.dashicons-menu-alt (f10b)`
- `.dashicons-rest-api (f124)`
- `.dashicons-yes-alt (f12a)`
- `.dashicons-tide (f10d)`

These icons were added to the `.ttf, ` and `.eot` font files, as well as the SVG sprite. However, they were not added to the `.woff` font file. The new `dashicons.woff2` file should be utilized instead.

For instances where IE<11 needs to be supported, the `.woff` file will remain for backwards compatibility. However, if the new icons are needed in those scenarios, the WOFF format is now included as embedded within the `dashicons.css`.

Props EmpireOfLight, liljimmi, jaymanpandya, netweb, melchoyce, joen, folletto, nateallen, bahia0019, JeffPaul, desrosj, cathibosco1.
Fixes #41074. 

git-svn-id: https://develop.svn.wordpress.org/trunk@44940 602fd350-edb4-49c9-b593-d223f7449a82

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