Fix integration filtering in AwsAccount selector

[justinas]

After https://github.com/gravitational/teleport/pull/40998 added a new integration kind (azure-oidc), the selector for AWS integration to use in the Discover flow stopped working (would display an empty list, crash when user attempts to type in the name manually). This seems to be because the existing code maps unknown integration types to undefined (by an implicit return if the kind does not match aws-oidc).

This fixes this by filtering for only aws-oidc as a separate step.