tdf#121780: com.sun.star.comp.sfx2.BackingComp needs to be registered always

...instead of never (as there is no handling of
org/openoffice/Office/ProtocolHandler-start.xcu in
officecfg/Configuration_officecfg.mk).  That install:module="start" included in
d930cefb "Startcenter: Refresh RecentDocsView
when select 'Clear list' menu option" was probably misguided cargo-cult-copying
from (meaningful) install:module="impress" that were already present in
officecfg/registry/data/org/openoffice/Office/ProtocolHandler.xcu.

Change-Id: I03ed0cf84b576597a7b88ee6627a12cedbca4960
Reviewed-on: https://gerrit.libreoffice.org/67224
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
(cherry picked from commit dbc92eab)
Reviewed-on: https://gerrit.libreoffice.org/67238Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>

officecfg/registry/data/org/openoffice/Office/ProtocolHandler.xcu

@@ -70,7 +70,7 @@
         <value>vnd.com.sun.star.comp.PresentationMinimizer:*</value>
       </prop>
     </node>
-    <node oor:name="com.sun.star.comp.sfx2.BackingComp" oor:op="replace" install:module="start">
+    <node oor:name="com.sun.star.comp.sfx2.BackingComp" oor:op="replace">
       <prop oor:name="Protocols">
         <value>vnd.org.libreoffice.recentdocs:*</value>
       </prop>