chore(deps): return Lighthouse to sigp unstable 73e4dc12

[shane-moore]

Problem, Evidence, and Context (Required)

• fix(deps): pin Lighthouse with #9959 for PTC data requests #1317 pinned every Lighthouse dependency to a personal fork branch (shane-moore/lighthouse 1513afc4) to carry Apply Beacon API amendments to payload attestation data endpoint lighthouse#9959 before it merged.
• #9959 merged upstream as 73e4dc12, which is the current Lighthouse unstable head, so the fork pin is no longer needed.

Change Overview (Required)

• All 18 Lighthouse dependencies return to sigp/lighthouse at 73e4dc120dfb49fbc5123d4fad42d935a94f368f. The lockfile diff is only those crates' source lines; no crates.io versions change.
• No Anchor source changes.

Risks, Trade-offs, and Mitigations (Required)

• The files #9959 touches are byte-identical between 1513afc4 and 73e4dc12, so PTC behavior from fix(deps): pin Lighthouse with #9959 for PTC data requests #1317 is unchanged.
• The bump also brings four upstream fork-choice commits (Remove ExecutionStatus predicates with no production callers lighthouse#10129, #10130, #10131, #10133) in beacon_node and consensus/{fork_choice,proto_array}. Anchor pulls proto_array in only as an indirect dependency and does not use that fork-choice code.
• Lighthouse's own Cargo.toml and Cargo.lock are unchanged between the two revs, so the mirrored [patch.crates-io] entries stay correct.

Validation (Required)

• git diff 1513afc4 73e4dc12 in Lighthouse: no changes under common/eth2, validator_client, or the beacon-node validator routes; only the fork-choice files above differ.
• make cargo-fmt-check, make lint, and cargo nextest run --release --workspace --no-fail-fast: passed, 993 tests.

Rollback (Required for behavior or runtime changes; optional otherwise)

Revert to the #1317 fork pin. No config or data impact.

Blockers / Dependencies (Optional)

• Keep the anchor/unstable-9ee3fd7-pr9959 branch on shane-moore/lighthouse while any tag or release candidate builds from 1513afc4.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.79%. Comparing base (664d9ae) to head (4b1bf80).

Additional details and impacted files

@@           Coverage Diff           @@
##             epbs    #1322   +/-   ##
=======================================
  Coverage   80.79%   80.79%           
=======================================
  Files         179      179           
  Lines       41224    41224           
=======================================
  Hits        33307    33307           
  Misses       7917     7917           

Flag	Coverage Δ
rust	80.79% <ø> (ø)

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