Remove 6.0 since it is end of life

https://github.com/redis/redis/security/policy

Author: yosifkit

6.0/alpine/Dockerfile

@@ -132,7 +132,7 @@ RUN set -eux; \
 		musl-dev \
 		openssl-dev \
 # install real "wget" to avoid:
-#   + wget -O redis.tar.gz https://download.redis.io/releases/redis-6.0.6.tar.gz
+#   + wget -O redis.tar.gz https://download.redis.io/releases/redis-x.y.z.tar.gz
 #   Connecting to download.redis.io (45.60.121.1:80)
 #   wget: bad header line:     XxhODalH: btu; path=/; Max-Age=900
 		wget \