docs: remove unneeded comments

Author: kenjis

system/Pager/PagerRenderer.php

@@ -122,8 +122,6 @@ public function hasPrevious(): bool
      * page before the current page, but is the page just before the
      * "first" page.
      *
-     * You MUST call hasPrevious() first, or this value may be invalid.
-     *
      * @return string|null
      */
     public function getPrevious()
@@ -162,8 +160,6 @@ public function hasNext(): bool
      * page after the current page, but is the page that follows the
      * "last" page.
      *
-     * You MUST call hasNext() first, or this value may be invalid.
-     *
      * @return string|null
      */
     public function getNext()