Update create-alias.rst

[phillisf]

Modified explanation text.

Removed 'alias/' from sentence beginning "Alias names must begin with..." to line up with wording in our documentation [1].

Removed the reference to the Decrypt API operation as this is not related to modifying an alias [2].

[1] https://docs.aws.amazon.com/awscloudtrail/latest/userguide/KMS-key-naming-requirements.html
[2] https://docs.aws.amazon.com/kms/latest/APIReference/API_Decrypt.html

[juneb]

Thanks for catching that cut/paste error. I used it when I was learning to add links in RST.

Let's fix that language. We can't say "alias names must begin with 'alias/'" and then say "Alias names cannot begin with 'aws.' Of course they can't. They have to begin with 'alias/'.

I suggest the following:

When specifying an alias in the CLI, type alias/ before the alias name. For example, "alias/myAlias". Alias names cannot begin with 'aws'; that name is reserved for AWS aliases.

This sentence appears in a few places, so I'll be sure to change all of them.