Fix Herd detection

Author: mpociot

src/Install/Herd.php

@@ -10,7 +10,7 @@ class Herd
 {
  public function isInstalled(): bool
  {
- if ($this->isWindowsPlatform()) {
+ if (! $this->isWindowsPlatform()) {
  return file_exists('/Applications/Herd.app/Contents/MacOS/Herd');
  }