DBus permissions missing from LO flatpak

...after 243d743d "solenv/flatpak-manifest.in:
incorporate upstream sandboxing improvements", causing
<https://github.com/flathub/org.libreoffice.LibreOffice/issues/3> "Doesn't open
files in network shares".

Change-Id: I15d7a170b3ffaf6092ff4d2fe4e93b1dcfd32b0b
(cherry picked from commit 95fbb490)
Reviewed-on: https://gerrit.libreoffice.org/45413Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

solenv/flatpak-manifest.in

@@ -393,6 +393,7 @@
         "--socket=pulseaudio",
         "--filesystem=host",
         "--env=LIBO_FLATPAK=1",
-        "--own-name=org.libreoffice.LibreOfficeIpc0"
+        "--own-name=org.libreoffice.LibreOfficeIpc0",
+        "--talk-name=org.gtk.vfs.*"
     ]
 }