tests: Correct includes ordering.

Spotted by korli.

src/tests/add-ons/kernel/partitioning_systems/PartitioningSystemsTest.cpp

@@ -8,9 +8,9 @@
 #include <fcntl.h>
 #include <limits.h>
 #include <stdio.h>
-#include <unistd.h>
-#include <string.h>
 #include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
 #include <map>
 #include <vector>

src/tests/system/kernel/device_manager/playground/specific_video_driver.cpp

@@ -6,9 +6,10 @@
 
 #include "bus.h"
 
+#include <string.h>
+
 #include <KernelExport.h>
 #include <PCI.h>
-#include <string.h>
 
 
 #define DRIVER_MODULE_NAME "drivers/graphics/specific_driver/driver_v1"