Changed recommendation to instance type in docs to a smaller one

What does this MR do?

Changed recommendation to instance type to a smaller one.

For such an easy task it is not needed to have 1 GB RAM, 0.5 is enough with 68% memory usage for most of the time. t4g.nano is cheaper and has more powerfull CPU (2 vCPUs ARM).

Related issues

none

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• Follow the Documentation Guidelines and Style Guide.
• If you have developer access or higher (for example, GitLab team members or Core Team members)
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When applicable:

• Update the permissions table.
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• Add GitLab's version history note(s).
• Add/update the feature flag section.
• If you're changing document headings, search docs/* for old headings and replace them with the new ones to avoid broken anchors.

Review checklist

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