Cleanup: Remove 'BKE_library.h' include from 'BKE_main.h'

That kind of implicit includes should really only be done when totally,
absolutely necessary, and ideally only with rather simple 'second-level'
headers.

Otherwise not being explicit with includes always end up biting in
unexpected ways...

source/blender/python/generic/bpy_internal_import.c

@@ -43,9 +43,10 @@
 #include "BLI_string.h"
 #include "BLI_utildefines.h"
 
+#include "BKE_library.h"
+#include "BKE_main.h"
 /* UNUSED */
 #include "BKE_text.h"  /* txt_to_buf */
-#include "BKE_main.h"
 
 #include "py_capi_utils.h"