bug#45901: GNOME Fonts takes about 20 seconds to display fonts

[Luis Felipe]

## Steps to reproduce

The following steps assume you are using Guix System with GNOME desktop.

1. Open the command prompt (ALT+F2)
2. Run gnome-font-viewer


## Expected result

GNOME Fonts starts and displays the fonts available (system and user fonts?) 
with their corresponding names and thumbnails.


## Unexpected result

+ GNOME Fonts starts, but the font view is empty and there is no visual sign of 
content being loaded.
+ The fonts are listed after waiting for about 20 seconds.
+ The fonts have no preview thumbnails (I heard Christopher Baines was looking 
into this particular issue)


## System information

GNOME 3.34.2
GNOME Fonts (gnome-font-viewer) 3.30.0
GNU Guix 5b785b2
On Hard Disk Drive


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Luis Felipe López Acevedo
https://luis-felipe.gitlab.io/