remove redundant "/"

This "/" is not needed as CMake adds this automatically
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 159fcce..95bdf68 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -269,4 +269,4 @@
 add_test(NAME ListTags COMMAND SelfTest --list-tags)
 set_tests_properties(ListTags PROPERTIES PASS_REGULAR_EXPRESSION "[0-9]+ tags")
 
-install(DIRECTORY "single_include/" DESTINATION "include/catch/")
+install(DIRECTORY "single_include/" DESTINATION "include/catch")