Correct typo in elasticache_replication_group regarding number of all…

…owed secondary replica groups (#40120)

Prior typo was confusing and had no semantic meaning. Updated to be accurate per AWS documentation

https://docs.aws.amazon.com/AmazonElastiCache/latest/dg/Redis-Global-Datastores-Getting-Started.html

The above documentation from AWS states:
"You can set up replication for a primary cluster from one AWS Region to a secondary cluster in up to two other AWS Regions.
Note: The exception to this are China (Beijing) Region and China (Ningxia) regions, where replication can only occur between the two regions."

website/docs/r/elasticache_replication_group.html.markdown

@@ -130,7 +130,7 @@ for full details on using Replication Groups.
 
 ### Creating a secondary replication group for a global replication group
 
-A Global Replication Group can have one one two secondary Replication Groups in different regions. These are added to an existing Global Replication Group.
+A Global Replication Group can have up to two secondary Replication Groups in different regions. These are added to an existing Global Replication Group.
 
 ```terraform
 resource "aws_elasticache_replication_group" "secondary" {