docs: 📚 Improve titles on header templates

[MartaPintoTeixeira]

Description

At the moment it is not obvious what to expect from the header templates.
This ticket is to review the titles in the header storys and rewrite them so they make more sense and are more clear for user. Consistency should be taken into consideration.

https://solid-design-system.fe.union-investment.de/docs/?path=/docs/templates-header-navigation--docs

Where to put the documentation

In header template from figma and code

DoR

• Item has business value
• Item has been estimated by the team
• Item is clear and well-defined
• Item dependencies have been identified