change include genode/env to an import (#20721)

* change `include genode/env` to an import 

ref 0b262e9496 (diff-8718bd20d8)

* fixes comments

lib/genode/env.nim

@@ -17,7 +17,7 @@
 #
 
 when not defined(genode):
-  {.error: "Genode only include".}
+  {.error: "Genode only module".}
 
 type
   GenodeEnvObj* {.importcpp: "Genode::Env", header: "<base/env.h>", pure.} = object

lib/pure/asyncdispatch.nim

@@ -1172,7 +1172,7 @@ else:
   when declared(posix.accept4):
     from posix import accept4, SOCK_CLOEXEC
   when defined(genode):
-    include genode/env # get the implicit Genode env
+    import genode/env # get the implicit Genode env
     import genode/signals
 
   const