Re-enable threading for formula groups for now.

As agreed at the ESC - lets see how this goes for 6.1

This reverts commit 4696d372.

Change-Id: Ic2be53c53dd7573972cd54c390443dc136739b6c
Reviewed-on: https://gerrit.libreoffice.org/54774Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

officecfg/registry/schema/org/openoffice/Office/Calc.xcs

@@ -1455,7 +1455,7 @@
           <info>
             <desc>Whether to use threaded calculation of formula groups when applicable.</desc>
           </info>
-          <value>false</value>
+          <value>true</value>
 	</prop>
 	<!-- Note: The default values below probably must correspond
 	to those assigned in setOpenCLConfigToDefault() in