[Serverless]: Change `Elastic serveless documentation` to `Elastic Cloud Serverless`

[KOTungseth]

Serverless Docs

Welcome to Elastic Serverless

Description

On Welcome to Elastic serverless documentation , make the following changes to the title:

• Instead of Elastic serverless, use Elastic Cloud Serverless
• Since this page lives at elastic.co/docs, avoid redundancy by removing documentation

Final title would appear as Elastic Cloud Serverless.

Resources and additional context