fix: 🤔 sd-text area help-text and error messages fixes

[MartaPintoTeixeira]

Current behavior

Problems:
1 ) The margin between the help-text and the text area and the margin between the error message and the text area is not consistent. will create a ticket to solve this issue in both figma and dev.
2 ) Help-text is visible in all screenshots:
https://solid-design-system.fe.union-investment.de/docs/?path=/story/components-sd-textarea-screenshots-sd-textarea--default
3 ) Label not showing:
https://solid-design-system.fe.union-investment.de/docs/?path=/story/components-sd-textarea-screenshots-sd-textarea--combination

Expected behavior

Solution:
1 ) figma: change it to margin-top 4 - DONE #1662
code: use the same margin you use for "error messages" in sd-input
2 ) Hide help-text in all screenshots execpt for "validation"
3 ) Show label (it is mandatory)

Steps to reproduce

Technical Information

DoR

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

DoD

• Documentation has been created/updated (if applicable)
• Migration Guide has been created/updated (if applicable)
• Relevant E2E tests (Features, A11y, Bug fixes) are created/updated
• Relevant stories (Features, A11y) are created/updated
• Implementation works successfully on feature branch