Revert "dtls.c: fix memory leak in dtls_free_context()"

This reverts commit 12cb03a6a150fb4edae2d696b4305b82a10926f3.

netq_delete_all() is most likely called too late because the peer
already have been destroyed.
diff --git a/dtls.c b/dtls.c
index e11a57b..fc7016a 100644
--- a/dtls.c
+++ b/dtls.c
@@ -3986,9 +3986,6 @@
     }
   }
 
-  if (ctx->sendqueue != NULL) {
-    netq_delete_all(&ctx->sendqueue);
-  }
   free_context(ctx);
 }