Fix the return type of OC_Template->fetchPage() to be string only

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

build/psalm-baseline.xml

@@ -6069,11 +6069,6 @@
       <code>OC_User::getUser()</code>
     </InvalidScalarArgument>
   </file>
-  <file src="lib/private/legacy/OC_Template.php">
-    <ImplementedReturnTypeMismatch occurrences="1">
-      <code>boolean|string</code>
-    </ImplementedReturnTypeMismatch>
-  </file>
   <file src="lib/private/legacy/OC_User.php">
     <UndefinedClass occurrences="1">
       <code>\Test\Util\User\Dummy</code>
@@ -6155,14 +6150,6 @@
   <file src="lib/public/AppFramework/Http/Template/PublicTemplateResponse.php">
     <InvalidScalarArgument occurrences="1"/>
   </file>
-  <file src="lib/public/AppFramework/Http/TemplateResponse.php">
-    <InvalidReturnStatement occurrences="1">
-      <code>$template-&gt;fetchPage($this-&gt;params)</code>
-    </InvalidReturnStatement>
-    <InvalidReturnType occurrences="1">
-      <code>string</code>
-    </InvalidReturnType>
-  </file>
   <file src="lib/public/AppFramework/Http/ZipResponse.php">
     <InvalidArrayAccess occurrences="5">
       <code>$resource['size']</code>

lib/private/legacy/OC_Template.php

@@ -171,7 +171,7 @@ class OC_Template extends \OC\Template\Base {
 
 	/**
 	 * Process the template
-	 * @return boolean|string
+	 * @return string
 	 *
 	 * This function process the template. If $this->renderAs is set, it
 	 * will produce a full page.