[BUGFIX] Replace TSFE call for page type

[sebkln]

What this pr does

This change replaces the outdated {TSFE:type} call for Open Search.
It prevents "Undefined property" PHP warnings for these calls, which are logged in the TYPO3 log.

How to test

1. Import the TypoScript template for Open Search from EXT:solr in the installation

2. Open the URL found in the href attribute of the following HTML tag

	<link rel="search"
		  type="application/opensearchdescription+xml"
		  href="https://www.example.org/?type=7567"
		  title="Website Search"
	/>

3. It downloads an unnamed XML file containing the OpenSearchDescription. The page type in the template attribute should be properly replaced:

	<Url type="application/opensearchdescription+xml"
		 rel="self"
		 template="https://www.example.org/index.php?type=7567&amp;L=0" />

Fixes: #4407