Remove CTest include

Without this include, CTest can still be run. Removing this cleans up MSVC
solution explorer, as CTestDashboardTargets (Continuous, Experimental,
Nightly and NightlyMemoryCheck) no longer show up
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b9ab7b0..907dba8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,7 +10,6 @@
 include(GNUInstallDirs)
 include(CheckIncludeFiles)
 include(CMakePackageConfigHelpers)
-include(CTest)
 
 # Build options
 option(BUILD_SHARED_LIBS "Build shared library" OFF)