Remove stellar/winget-pkgs (fork of microsoft/winget-pkgs) from Stellar

[lingxiaolyu191231]

Remove stellar/winget-pkgs (fork of microsoft/winget-pkgs) from Stellar

What

Adds a migration removing https://github.com/stellar/winget-pkgs from the
Stellar ecosystem.

reprem Stellar https://github.com/stellar/winget-pkgs

Why

stellar/winget-pkgs is a fork of microsoft/winget-pkgs (the Windows
Package Manager manifest repo), created under the Stellar org to publish a
package to winget — standard practice. Because the fork carries upstream's full
contributor history, it pulls a large number of Windows-packaging contributors
into Stellar's developer counts:

• ~1,440 active developers in the last 90 days, but only 2 stars
• 1,440 of those 1,444 appear in no other Stellar repo
• ≈27% of Stellar's recent active developers in the current snapshot
  (20260715T125411)

None of these contributors do crypto work on Stellar — the attribution is purely
an artifact of the fork relationship.

Precedent

This mirrors the prior removal of the equivalent Nethermind fork in
migrations/2025-05-01T112748_mutations:

reprem Ethereum https://github.com/NethermindEth/winget-pkgs
reprem Nethermind https://github.com/NethermindEth/winget-pkgs

Verification

• open-dev-data validate passes.
• open-dev-data export -e Stellar contains the repo before this migration
  and no longer contains it after (A/B checked).