[6.1] Restrict approver policy to 6.1 branch

[paulmedynski]

Description

• Restricted the approver policy to the ADO 6.1 branch.

[Copilot]

Pull Request Overview

This PR restricts the approver count policy to apply only to the ADO 6.1 branch, removing the policy from main and other release branches.

Key Changes:

• Limited branch scope from multiple branches (main, 5.1, 5.2, 6.0) to only the 6.1 release branch
• Updated branch name format from refs/heads/internal/release/6.1 to internal/release/6.1 for consistency with other pipeline configurations
• Updated policy description and display name to reflect 6.1-specific scope

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.82%. Comparing base (5200419) to head (0df6832).
⚠️ Report is 12 commits behind head on release/6.1.

Additional details and impacted files

@@               Coverage Diff                @@
##           release/6.1    #3782       +/-   ##
================================================
+ Coverage        66.69%   90.82%   +24.13%     
================================================
  Files              279        6      -273     
  Lines            61764      316    -61448     
================================================
- Hits             41192      287    -40905     
+ Misses           20572       29    -20543     

Flag	Coverage Δ
addons	90.82% <ø> (ø)
netcore	?
netfx	?

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