main/postmarketos-hidden-desktop-entries: add FF-ESR safe mode (MR 1448)

Firefox ESR Safe Mode has another name for the .desktop file, hide it as
well.

main/postmarketos-hidden-desktop-entries/APKBUILD

 # Maintainer: Oliver Smith <ollieparanoid@postmarketos.org>
 pkgname=postmarketos-hidden-desktop-entries
-pkgver=1.0
+pkgver=1.1
 pkgrel=0
 pkgdesc="Hide useless .desktop icons (vim, htop, Firefox safe mode, ...)"
 url="https://postmarketos.org"
@@ -11,6 +11,7 @@ builddir="$srcdir/"
 
 # Find original .desktop files in /usr/share/applications
 _hidden="
+	firefox-safe
 	htop
 	nvim
 	org.gnome.Cheese