message: [cli] Fix tests for `.gitignore` append during project link
  Fixes tests from
diff: @@ -2701,7 +2701,7 @@ test('should show prompts to set up project during first deploy', async t => {
  // Ensure .gitignore is created
  t.is(
  (await readFile(path.join(directory, '.gitignore'))).toString(),
  - '.vercel'
  + '.vercel\n'
  );
  // Ensure .vercel/project.json and .vercel/README.txt are created
  @@ -3321,7 +3321,7 @@ test('[vc link] should show prompts to set up project', async t => {
  t.is(output.exitCode, 0, formatOutput(output));
  // Ensure .gitignore is created
  - t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel');
  + t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel\n');
  // Ensure .vercel/project.json and .vercel/README.txt are created
  t.is(
  @@ -3355,7 +3355,7 @@ test('[vc link --confirm] should not show prompts and autolink', async t => {
  t.regex(stderr, /Linked to /m);
  // Ensure .gitignore is created
  - t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel');
  + t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel\n');
  // Ensure .vercel/project.json and .vercel/README.txt are created
  t.is(
  @@ -3439,7 +3439,7 @@ test('[vc dev] should show prompts to set up project', async t => {
  await waitForPrompt(dev, chunk => chunk.includes('Linked to'));
  // Ensure .gitignore is created
  - t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel');
  + t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel\n');
  // Ensure .vercel/project.json and .vercel/README.txt are created
  t.is(
  @@ -3505,7 +3505,7 @@ test('[vc link] should show project prompts but not framework when `builds` defi
  t.is(output.exitCode, 0, formatOutput(output));
  // Ensure .gitignore is created
  - t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel');
  + t.is((await readFile(path.join(dir, '.gitignore'))).toString(), '.vercel\n');
  // Ensure .vercel/project.json and .vercel/README.txt are created
  t.is(
  