UnoApiTest don't dispose mxDesktop

It breaks CppunitTest_sc_outlineobj,
which runs several setUp/tearDown several times?

Change-Id: Ic81324d150aa64135cdbedc4cb99f78d415da1aa

test/source/unoapi_test.cxx

@@ -31,7 +31,6 @@ void UnoApiTest::setUp()
 
 void UnoApiTest::tearDown()
 {
-    uno::Reference< lang::XComponent >( mxDesktop )->dispose();
     test::BootstrapFixture::tearDown();
 }