[8.15] Update port assignments from 'Fleet' to 'Kibana (Fleet)' (backport #1276)

[mergify]

From a Slack thread with @jeanfabrice, this updates the default port settings on the three pages below to refer to "Kibana (Fleet)" rather than "Fleet":

• Deploy on Elastic Cloud
• Deploy on premises and self-managed
• Deploy Fleet Server on premises and Elasticsearch on Cloud

For example:

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This is an automatic backport of pull request #1276 done by [Mergify](https://mergify.com).

[github-actions]

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