message: cli: document yarn install workaround and tweak upgrade helper messaging
diff: @@ -430,7 +430,7 @@ export async function bumpBackstageJsonVersion(version: string) {
  yellow(
  `Upgraded from release ${green(prevVersion)} to ${green(
  version,
  - )}, please review the app changes:`,
  + )}, please review these template changes:`,
  ),
  );
  console.log();
  @@ -466,6 +466,9 @@ async function runYarnInstall() {
  await run('yarn', ['install'], {
  env: {
  FORCE_COLOR: 'true',
  + // We filter out all of the npm_* environment variables that are added when
  + // executing through yarn. This works around an issue where these variables
  + // incorrectly override local yarn or npm config in the project directory.
  ...Object.fromEntries(
  Object.entries(process.env).map(([name, value]) =>
  name.startsWith('npm_') ? [name, undefined] : [name, value],
  