Drop dead stewardship labels (InDesign, ChangesRequested)

[samvaity]

Part of #45437.

Delete the two dead stewardship labels and rely on GitHub's native "changes requested"
review state instead:

• APIStewardshipBoard-InDesign (1 PR ever labeled)
• APIStewardship-ChangesRequested (9 PRs ever labeled)

No workflow code reads either label, so this is zero-risk and independent of the other
sub-issues.

[samvaity]

Done. Deleted both dead labels (no automation read them):

• APIStewardshipBoard-InDesign (1 PR)
• APIStewardship-ChangesRequested (9 PRs)

"Changes requested" is now tracked via GitHub's native review state.