Apply suggestions from code review

Co-Authored-By: Ihor Sviziev <ihor-sviziev@users.noreply.github.com>

Author: krzksz

app/code/Magento/Theme/Controller/Result/JsFooterPlugin.php

@@ -48,7 +48,8 @@ public function beforeSendResponse(Http $subject)
         );
 
         if ($isEndBodyTagFound && $shouldMoveJsToBottom) {
-            if ($scripts = $this->extractScriptTags($content)) {
+            $scripts = $this->extractScriptTags($content)
+            if ($scripts) {
                 $content = str_replace($bodyEndTag, "$scripts\n$bodyEndTag", $content);
                 $subject->setContent($content);
             }
@@ -60,7 +61,7 @@ public function beforeSendResponse(Http $subject)
      *
      * @param string $content
      */
-    public function extractScriptTags(&$content)
+    private function extractScriptTags(&$content): string
     {
         $scripts = '';
         $scriptOpen = '<script';