-Werror,-Wself-assign

Looks like this was a typo ever since the code's introduction in
77cc7cfa "INTEGRATION: CWS rptwizard01" (and
then changed again in d1ea6ecd "replace <<= with
assign for <<= with rhs Any").

Change-Id: I8c4fa3ddb651400b9bf65395e8b6ff946c74abf5
Reviewed-on: https://gerrit.libreoffice.org/52813Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

reportdesign/source/core/api/ReportDefinition.cxx

@@ -1607,7 +1607,7 @@ void SAL_CALL OReportDefinition::load( const uno::Sequence< beans::PropertyValue
 
     uno::Any aStorageSource;
     if ( xStream.is() )
-        aStorageSource = aStorageSource;
+        aStorageSource <<= xStream;
     else if ( !sURL.isEmpty() )
         aStorageSource <<= sURL;
     else