Hide SSH signature from the tag's message

What does this MR do and why?

Contributes to #438825 (closed)

Problem

The SSH signature is visible in tag's message body.

Solution

Remove the signature text same way as it's done for other signature types.

References

• SSH Signed tags look ugly, the signature is not... (#438825 - closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Clone the example repository into GDK
2. Visit tags page
3. SSH signature context should be missing in the tag's message body

MR acceptance checklist

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Related to #438825 (closed)