Updated core-test submodule

Also, set EDITORCONFIG_CMD_IS_TARGET false: our test executable
is pre-built, not made by cmake.

Author: cxw42

.gitmodules

@@ -3,5 +3,4 @@
 	url = https://github.com/editorconfig/editorconfig-plugin-tests.git
 [submodule "core_tests"]
 	path = tests/core/tests
-	url = https://github.com/cxw42/editorconfig-core-test.git
-	branch = cxwtest
+	url = https://github.com/editorconfig/editorconfig-core-test.git

tests/core/CMakeLists.txt

@@ -45,6 +45,7 @@ if(NOT WIN32)
 else()
     set(EDITORCONFIG_CMD "${CMAKE_SOURCE_DIR}/editorconfig.bat")
 endif()
+set(EDITORCONFIG_CMD_IS_TARGET FALSE)
 
 add_subdirectory(tests)