fix(ci): bump a2ml-validate-action SHA to pick up contractile-shape fix (#15)

Picks up hyperpolymath/a2ml-validate-action#9 which fixes the validator's false-positive on contractile-shape .a2ml files (Trustfile, Intentfile, etc. using @directive: syntax). Was blocking every Dependabot PR in this repo with 'Missing required identity field'.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: hyperpolymath