Removed heroku button from quickstart and fixed list index from Next.js documentation

Editor assessment

This subject tries to carry two unrelated changes — removing the Heroku button from the quickstart and fixing a list index in the Next.js docs — which violates the one-commit-one-logical-change spirit and pushes the line well past 72 characters, risking truncation in GitHub views. 'Removed' and 'fixed' are past tense where the imperative 'remove ... and fix ...' is conventional, though pairing two verbs in one subject is itself a smell that the work should have been split. The body's two bullets mirror the subject without adding detail. Type docs: is correct and no breaking markers are needed. Structure is valid, so tooling copes, but the changelog entry is cluttered; two short, separate commits would have produced far cleaner release notes and history.