Docs: Fix warning in metrics documentation

[leandrodamascena]

What were you searching in the docs?

The rendering of this banner is wrong as the line below is missing a tab.

Is this related to an existing documentation section?

https://awslabs.github.io/aws-lambda-powertools-typescript/latest/core/metrics/#manually

How can we improve?

Fix the format. I'm sending the fix.

Got a suggestion in mind?

No response

Acknowledgment

• I understand the final update might be different from my proposed suggestion, or refused.

[dreamorosi]

Thanks for the fix, appreciate it!