test(uri_log): satisfy cpplint build/include_subdir for httpserver.hpp

cpplint flags bare "httpserver.hpp" with build/include_subdir [4].
Match the convention used by every other test file in the repo and
prefix the include with "./" so cpplint considers the directory
explicit.

Author: etr

test/unit/uri_log_test.cpp

@@ -20,7 +20,7 @@
 
 #include <string>
 
-#include "httpserver.hpp"
+#include "./httpserver.hpp"
 #include "httpserver/details/modded_request.hpp"
 
 #include "./littletest.hpp"