swupdate: remove empty line

Reported by Yann E. Morin running:

```
    $ ./utils/check-package package/swupdate/swupdate.mk
    package/swupdate/swupdate.mk:42: consecutive empty lines
    140 lines processed
    1 warnings generated
```

Reported-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/swupdate/swupdate.mk

@@ -39,7 +39,6 @@ else
 SWUPDATE_MAKE_ENV += HAVE_LIBCURL=n
 endif
 
-
 ifeq ($(BR2_PACKAGE_HAS_LUAINTERPRETER),y)
 SWUPDATE_DEPENDENCIES += luainterpreter host-pkgconf
 # defines the base name for the pkg-config file ("lua" or "luajit")