fix(cmd): hard-code Inter to v3.19 release

The new major release has a different file structure, which breaks
extraction process.  Moreover, I'm curious about the differences between
the two versions, so I'll spend some time on it later.

cmd/userstyles-fonts/main.go

@@ -17,7 +17,7 @@ import (
 )
 
 var (
-	releaseURL = "https://api.github.com/repos/rsms/inter/releases/latest"
+	releaseURL = "https://api.github.com/repos/rsms/inter/releases/44888689" // v3.19
 	distDir    = path.Join("web", "static", "fonts")
 )