Merge pull request #553 from ghutchis/updated-qttesting

Use lower-case QtTesting library link

Author: ghutchis

avogadro/CMakeLists.txt

@@ -225,7 +225,7 @@ else()
   set_target_properties(avogadro PROPERTIES OUTPUT_NAME "avogadro2")
 endif()
 if(ENABLE_TESTING)
-  target_link_libraries(avogadro QtTesting)
+  target_link_libraries(avogadro qttesting)
 endif()
 if(QT_VERSION EQUAL 6)
   target_link_libraries(avogadro Qt6::OpenGL Qt6::OpenGLWidgets)