Heorku deploy failure

Editor assessment

The subject names the defect, a Heroku deployment failure, though the transposed 'heorku' is the first thing a reader sees, and fix is the right type. The body's bullets add one real fact, the default stack was set to heroku-20, which is the actual remedy, but nothing explains what about the previous stack failed. No scope, no footers. The trailing pull-request number is conventional, and the bullet structure is acceptable squash residue. Hygiene besides the typo is passable. Understandable, valid, and thin.