• No need for a horizontal line to be randomly there.
• Get rid of GtkFrames that enclose only one element.
  Seriously, they are cancer. Use them properly!
• … and while I’m here, use a stock label for the Search button.
  I noticed the associated help page not using the “Go” name.

Change-Id: Id196d8d970a219285c5cc606ab9b4327cdce2e91
Reviewed-on: https://gerrit.libreoffice.org/62238
Tested-by: Jenkins
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>