codec: fix package name to codec

codec/codecgen.go

@@ -1,6 +1,12 @@
 // +build codecgen generated
 
-package codecgen
+package codec
+
+// this file is here, to set the codecgen variable to true
+// when the build tag codecgen is set.
+//
+// this allows us do specific things e.g. skip missing fields tests,
+// when running in codecgen mode.
 
 func init() {
 	codecgen = true