Don't even bother to introduce unused variables

With <https://gerrit.libreoffice.org/c/core/+/152157> "More conservative
SAL_WARN_UNUSED to avoid -Werror,-Wunused-private-field", these two cases would
have started to cause "unused variable declaration [loplugin:casttovoid]"
(because the call to isWarnUnusedType in compilerplugins/clang/casttovoid.cxx
would no longer return true).  Just avoid that by not introducing the variables
in the first place.

Change-Id: I3d2b085082555d1765fbd32045b5157deb0af67e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/152158
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

sc/qa/extras/scdatapilotfieldobj.cxx

@@ -96,8 +96,7 @@ uno::Reference<uno::XInterface> ScDataPilotFieldObj::init()
 
     uno::Reference<sheet::XDataPilotTablesSupplier> xDPTS(xSheet, uno::UNO_QUERY_THROW);
     uno::Reference<sheet::XDataPilotTables> xDPT(xDPTS->getDataPilotTables(), uno::UNO_SET_THROW);
-    uno::Sequence<OUString> aElementNames = xDPT->getElementNames();
-    (void)aElementNames;
+    (void)xDPT->getElementNames();
 
     uno::Reference<sheet::XDataPilotDescriptor> xDPDsc(xDPT->getByName("DataPilot1"),
                                                        uno::UNO_QUERY_THROW);

test/source/sheet/xdatabaserange.cxx

@@ -125,8 +125,7 @@ void XDatabaseRange::testGetFilterDescriptor()
 void XDatabaseRange::testGetImportDescriptor()
 {
     uno::Reference<sheet::XDatabaseRange> xDBRange(init("ImportDescriptor"), UNO_QUERY_THROW);
-    uno::Sequence<beans::PropertyValue> xImportDescr = xDBRange->getImportDescriptor();
-    (void)xImportDescr;
+    (void)xDBRange->getImportDescriptor();
 }
 
 void XDatabaseRange::testRefresh()