Make gnome-shell-clock-preferences work again

Thanks Owen and Colin for debugging this:

<davidz> does anyone have a clue about this cryptic error message: http://fpaste.org/aWgh/ ?
<owen> davidz: well, I'd guess some sort of syntax error...
<walters> hmm
 possibly but unlikely fallout from my js versioning
<owen> oh, it's happening here too
 walters: exactly
 Adding --js-version=1.8 to the wrapper script fixes
 walters: I thought you were defaulting to allowing extensions?
<walters> actually, let's do that now anyways

Signed-off-by: David Zeuthen <davidz@redhat.com>

src/gnome-shell-clock-preferences.in

@@ -18,7 +18,7 @@ uiFile="$uiDir/clock-preferences.ui"
 export GJS_PATH="$jsDir"
 export GSETTINGS_SCHEMA_DIR="$schemaDir"
 
-@GJS_CONSOLE@ -c "const ClockPreferences = imports.prefs.clockPreferences;
+@GJS_CONSOLE@ --js-version 1.8 -c "const ClockPreferences = imports.prefs.clockPreferences;
 ClockPreferences.main({ progName: '$progName',
                         uiFile: '$uiFile',
                         localeDir: '$localeDir' });"