Issue #3311472 Set minimum stability for form

Closes #3311472

src/Validator/VersionPolicyValidator.php

@@ -87,14 +87,20 @@ final class VersionPolicyValidator implements EventSubscriberInterface {
       $rules[] = MajorVersionMatch::class;
       // ...and it must be a known, secure, installable release...
       $rules[] = TargetVersionInstallable::class;
-      // ...and must be either a release candidate, or stable.
-      $rules[] = TargetVersionNotPreRelease::class;
+      // @todo Remove the need to check for the stage instance in
+      //   https://drupal.org/i/3398782.
+      if (!$stage instanceof ConsoleUpdateStage) {
+        // ...and must be either a release candidate, or stable.
+        $rules[] = TargetVersionNotPreRelease::class;
+      }
     }
 
     // If this is a cron update, we may need to do additional checks.
     if ($stage instanceof ConsoleUpdateStage) {
       $mode = $this->cronUpdateRunner->getMode();
 
+      // @todo Remove the need to check if cron updates are disabled in
+      //   https://drupal.org/i/3398782.
       if ($mode !== CronUpdateRunner::DISABLED) {
         // If cron updates are enabled, the installed version must be stable;
         // no alphas, betas, or RCs.