[5.4] Fix return type for App getDocument, getLanguage methods#46238

muhme merged 2 commits intojoomla:5.4-devjoomla/joomla-cms:5.4-devfrom

Fedik:fix-app-return-type-doc-langFedik/joomla-cms:fix-app-return-type-doc-langCopy head branch name to clipboard