libreoffice: fix gstreamer paths

Libreoffice uses gstreamer for for audio and video within impress. If
the correct gstreamer plugins are not available (e.g. because the plugin
path is not set correctly), then adding such media will not play and can
even temporarily hang the interface.

This commit fixes incorrect and missing paths in the current libreoffice
wrapper:

- the gstreamer plugins are located in gstreamer-1.0 directories rather
  than girepository-1.0
- the default output of the gstreamer package only contains executables
  and not the plugins

pkgs/applications/office/libreoffice/default.nix

@@ -706,7 +706,7 @@ stdenv.mkDerivation (finalAttrs: {
       gst-plugins-base
       gst-plugins-good
       gst-plugins-ugly
-      gstreamer
+      gstreamer.out
     ];
     qmlPackages = [
       kdePackages.ki18n

pkgs/applications/office/libreoffice/wrapper.nix

@@ -54,7 +54,7 @@ let
       "--prefix"
       "GST_PLUGIN_SYSTEM_PATH_1_0"
       ":"
-      "${lib.makeSearchPath "lib/girepository-1.0" unwrapped.gst_packages}"
+      "${lib.makeSearchPath "lib/gstreamer-1.0" unwrapped.gst_packages}"
       "--suffix"
       "PATH"
       ":"