[12.x] Add missing @throws annotations to Encrypter class (#57451)

- Add @throws DecryptException to ensureTagIsValid() method
- Add @throws RuntimeException to previousKeys() method

These methods throw exceptions but were missing proper @throws annotations in their docblocks.

Author: sumaiazaman

src/Illuminate/Encryption/Encrypter.php

@@ -302,6 +302,8 @@ protected function validMacForKey(#[\SensitiveParameter] $payload, $key)
      *
      * @param  string  $tag
      * @return void
+     *
+     * @throws \Illuminate\Contracts\Encryption\DecryptException
      */
     protected function ensureTagIsValid($tag)
     {
@@ -359,6 +361,8 @@ public function getPreviousKeys()
      *
      * @param  array  $keys
      * @return $this
+     *
+     * @throws \RuntimeException
      */
     public function previousKeys(array $keys)
     {