Adjust the stemcell_name in the shared functions for Noble

[Milena-Encheva]

What is this change about?

This update modifies the logic in a shared-functions and bosh-upload-stemcell tasks to handle stemcell naming conventions more accurately.

Please provide contextual information.

The adjustment ensures that the suffix "go_agent" is not appended to the stemcell_name when using the "ubuntu-noble" os. This allows for more flexible use of stemcells based on their operating system.

Please check all that apply for this PR:

• introduces a new task
• changes an existing task
• changes the Dockerfile
• introduces a breaking change (other users will need to make manual changes when this is released)

Did you update the README as appropriate for this change?

• YES
• N/A

How should this change be described in release notes?

Improvement: Stemcell Naming
Adjusted naming logic to exclude "go_agent" for "ubuntu-noble" stemcells, aligning with OS-specific conventions.

What is the level of urgency for publishing this change?

• Urgent - unblocks current or future work
• Slightly Less than Urgent

Tag your pair, your PM, and/or team!

@dimivel

[dimivel]

LGTM