css.lang.XSingleServiceFactory must not be @deprecated

...which caused cppumaker to emit the corresponding C++ class as
SAL_DEPRECATED_INTERNAL (since 44ea5d1414 "Adding
SAL_DEPRECATED_INTERNAL to an implementation function is pointless"), which
caused compilers to emit warnings upon its legitimate uses in external
!LIBO_INTERNAL_ONLY code

Change-Id: I8043506cd11658164e68f8743702acbc1a8213f3
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/182832
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>

udkapi/com/sun/star/lang/XSingleServiceFactory.idl

@@ -25,10 +25,11 @@ module com {  module sun {  module star {  module lang {
 /** Factory interface to produce instances of an implementation
     of a service specification.
 
-    This interface is deprecated.  Please use XSingleComponentFactory.
+    This interface is mostly deprecated.  Please use XSingleComponentFactory.
+    However, it is still used for specific tasks, e.g. by com::sun::star::script::Invocation or
+    com::sun::star::configuration::SimpleSetUpdate.
 
     @see XInitialization
-    @deprecated
 */
 published interface XSingleServiceFactory: com::sun::star::uno::XInterface
 {