tests: move include of tests/tests.h outside of extern "C"

tests/unit/plugins/logger/test-logger-backlog.cpp

@@ -21,6 +21,8 @@
 
 #include "CppUTest/TestHarness.h"
 
+#include "tests/tests.h"
+
 extern "C"
 {
 #include <stdio.h>
@@ -34,9 +36,6 @@ extern void logger_backlog_display_line (struct t_gui_buffer *buffer,
                                          const char *line);
 }
 
-#include "tests/tests.h"
-
-
 TEST_GROUP(LoggerBacklog)
 {
 };