Update Multi-Repo Analysis Issue Text to Reflect Single-Repo Limit

## Context

The initial issue *"Code Quality: Configure CodeRabbit Multi-Repo Analysis (if applicable)"* (added in PR #90) contains wording that implies multiple linked repositories can be configured. However, the CodeRabbit configuration schema currently enforces `maxItems: 1` on `knowledge_base.linked_repositories`.

## Problem

The issue text references "repositories" / "repos" in plural, which may confuse contributors who try to add more than one entry and find it isn't supported yet.

## Suggested Fix

Once `linked_repositories` supports multiple items (planned), the wording can remain as-is. Until then, update the issue body to either:
- Use singular wording ("repository"), or
- Add a parenthetical note such as *(currently limited to one linked repository via `knowledge_base.linked_repositories`)*

## References
- PR: https://github.com/AOSSIE-Org/Template-Repo/pull/90
- Review comment: https://github.com/AOSSIE-Org/Template-Repo/pull/90#discussion_r2889253440

/cc @kpj2006