Update default version in Makefile (#556)

Update default version of apisix-ingress-controller in Makefile to be the latest version 1.0.0.
diff --git a/Makefile b/Makefile
index 70d1582..9c117bc 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@
 #
 default: help
 
-VERSION ?= 0.6.0
+VERSION ?= 1.0.0
 RELEASE_SRC = apache-apisix-ingress-controller-${VERSION}-src
 LOCAL_REGISTRY="localhost:5000"
 IMAGE_TAG ?= dev