prettier errors (as it says on the tin). The function syntax doesn’t comply with what the Prettier formatter expects to see.
For context, there was a switch in behavior from Prettier 1.9 to Prettier 2: Prettier 1.9 would by default avoid parentheses for arrow functions with a single parameters (where they are not technically needed); Prettier 2 would by default enforce them. See Options · Prettier. The Grafana codebase was updated to comply with this change in this commit.
All in all, I think you’re getting these errors because you’re trying to use Prettier 1.x to format a version of the Grafana codebase that’s been formatted according to Prettier 2.x standards. Unless your package lock files are out of sync with the Grafana repo, you should be able to fix this by (a) cleaning your Node development environment, and (b) running
yarn install --pure-lockfile
That said, your build log says you’re building “Version 7.2.2”, and the Prettier 2 change was implemented in v7.4.0, so it’s possible that different parts of your local codebase have not been updated in sync with upstream, which may be a tougher nut to crack.