Fix english in comment
@@ -6,7 +6,7 @@ ARG DIST=buster
# The build stage
# ---------------
FROM python:3.8-$DIST as build-stage
-# ARG DIST has to be defined again to made available inside this build stage.
+# ARG DIST is defined again to be made available in this build stage's scope.
# ref: https://docs.docker.com/engine/reference/builder/#understand-how-arg-and-from-interact
ARG DIST
