python,python3: fix recursive deps caused by dangling DEPENDS

For python `src` packages we should clear out the DEPENDS
to prevent recursive deps from happening.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

lang/python/python-package.mk

@@ -39,6 +39,7 @@ define PyPackage
 
   define Package/$(1)-src
     $(call Package/$(1))
+    DEPENDS:=
     TITLE+= (sources)
   endef
 

lang/python/python3-package.mk

@@ -38,6 +38,7 @@ define Py3Package
 
   define Package/$(1)-src
     $(call Package/$(1))
+    DEPENDS:=
     TITLE+= (sources)
   endef