Change the exemption issue label pinned to internal for stale issues

[yubiuser]

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What does this PR aim to accomplish?:
Change the exemption issue label pinned to internal for stale issues. We don't use the label pinned, but internal

[PromoFaux]

Pinned, in this case, means that the issue is pinned to the top of the page, not a label.

We can add internal as an additional, though, for sure.

[yubiuser]

Pinned, in this case, means that the issue is pinned to the top of the page, not a label.

Do you have any reference for this? I was looking for this, but the only case I found was after others explicitly added pinned as a label...

[PromoFaux]

Oh, no reference - all based on assumption.

[yubiuser]

Try searching for issues with label:pinned yields nothing, even though one is currently pinned...