Sync allow_rotated / allow_unparseable_crs tiers in geotiff_release_contract.md (#2389)

[brendancol]

Summary

• Update reader.allow_rotated and reader.allow_unparseable_crs from advanced to experimental in geotiff_release_contract.md so the contract page agrees with SUPPORTED_FEATURES and release_gate_geotiff.rst after the Epic: GeoTIFF release contract and feature tiering #2340 demotion.
• Also fix codec.jpeg from internal-only to internal_only so every tier string in the table is a verbatim runtime key, and align the matching section heading.
• Docs-only. No code change. Existing tier tests (test_supported_features_tiers_2137.py, test_release_gate_2321.py) still pass locally.

Closes #2389. Follow-up from #2381 / PR #2388.

Test plan

• pytest xrspatial/geotiff/tests/test_release_gate_2321.py xrspatial/geotiff/tests/test_supported_features_tiers_2137.py
• Sphinx build is unaffected (table rendering only).

[brendancol]

PR Review: Sync allow_rotated / allow_unparseable_crs tiers in geotiff_release_contract.md (#2389)

Four-line doc-sync PR. The two advanced → experimental rows match the explicit ask in the issue. The diff also catches a third tier-string mismatch in the same table (codec.jpeg: internal-only → internal_only). After the change, every key the contract page lists agrees with both SUPPORTED_FEATURES and release_gate_geotiff.rst.

Blockers (must fix before merge)

• None.

Suggestions (should fix, not blocking)

• No automated check pins geotiff_release_contract.md against SUPPORTED_FEATURES. The PR fixes the current drift but the same drift can re-appear the next time a key gets re-tiered in _attrs.py. test_release_gate_2321.py only parses the .rst gate page, not this .md contract page. Worth a follow-up to add a parity test that walks the markdown table and compares each row's tier column against SUPPORTED_FEATURES[key]. Out of scope for this PR, but the issue itself exists because that lock was missing.

Nits (optional improvements)

• The heading rename ### internal-only → ### internal_only (geotiff_release_contract.md:46) goes slightly past the issue's "two rows" wording. The heading is the tier label and the body prose already says internal_only, but it does change the MyST anchor. A repo-wide grep for #internal-only came back empty, so no link is broken. Flagging for traceability.
• geotiff_release_contract.md:52 still uses "internal-only" as an English compound adjective ("Do not build on internal-only features."). That is correct hyphenation in prose, not a tier string, so it should stay. Noting here so a future reviewer does not "fix" it.

What looks good

• Doc edit is small and contained; no unrelated changes pulled in.
• Commit message explains why (post-#2340 drift), not just what.
• Existing tier tests still pass locally.

Checklist

• Tier strings on every listed key now match SUPPORTED_FEATURES.
• Tier strings on every shared key now match release_gate_geotiff.rst.
• No code change. Runtime behaviour unchanged.
• No anchor / cross-reference breakage from the heading rename.
• No new tests needed (issue notes existing tests cover the source of truth).