CMake: Fix wrong policy number

CMakeLists.txt

@@ -52,9 +52,9 @@ endif(POLICY CMP0072)
 if(POLICY CMP0074)
 	cmake_policy(SET CMP0074 NEW)
 endif(POLICY CMP0074)
-if(POLICY CMP0074)
+if(POLICY CMP0092)
 	cmake_policy(SET CMP0092 NEW)
-endif(POLICY CMP0074)
+endif(POLICY CMP0092)
 
 project(RmlUi LANGUAGES C CXX VERSION 6.0)