[bug] Fix version 6.x and 7.0 in parameter group

[josacar]

Right now support for 6.x and 7.0 versions is broken in this module, as it's referencing an non-existing parameter group.

I went to the current AWS versions and I did a mapping with the parameter_group_family :

3.2.4 => redis3.2
3.2.6 => redis3.2
3.2.10 => redis3.2
4.0.10 => redis4.0
5.0.6 => redis5.0
6.0 => redis6.x
6.2 => redis6.x
6.x => redis6.x
7.0 => redis7

This is the tests I performed with the current code in repository:

❯ for version in 3.2.4 3.2.6 3.2.10 4.0.10 5.0.6 6.0 6.2 6.x 7.0; do
     echo "local.parameter_group_family_old" | TF_VAR_redis_version="$version" terraform console
   done

"redis3.2"
"redis3.2"
"redis3.2"
"redis4.0"
"redis5.0"
"redis6.x"
"redis6.x"
"redis6.x.x"
"redis7.x"

As you can see, 6.x and 7.0 versions are wrong ( last two lines )

With my path produces the following result:

❯ for version in 3.2.4 3.2.6 3.2.10 4.0.10 5.0.6 6.0 6.2 6.x 7.0; do
     echo "local.parameter_group_family" | TF_VAR_redis_version="$version" terraform console
   done

"redis3.2"
"redis3.2"
"redis3.2"
"redis4.0"
"redis5.0"
"redis6.x"
"redis6.x"
"redis6.x"
"redis7"

Which matches with the manual mapping in the beginning of the post.

@antonbabenko let me know if you need anything else.