Removes explicit GoogleTest include

Author: kwach

test/CMakeLists.txt

@@ -29,7 +29,6 @@ find_package(CURL REQUIRED)
 add_executable(httplib-test test.cc include_httplib.cc $<$<BOOL:${WIN32}>:include_windows_h.cc>)
 target_compile_options(httplib-test PRIVATE "$<$<CXX_COMPILER_ID:MSVC>:/utf-8;/bigobj>")
 target_link_libraries(httplib-test PRIVATE httplib GTest::gtest_main CURL::libcurl)
-include(GoogleTest)
 gtest_discover_tests(httplib-test)
 
 file(