[BUGFIX] Update invalid link to the TYPO3 documentation

This patch updates the link and points users to the new
documentation as the previous link became invalid. In
addition, the patch also slightly improves the wording
related to the TYPO3 Core upgrade function.

Resolves: #96702
Releases: main, 11.5
Change-Id: Ie267a6aa70cbb6aad80aa17f834571b8435ee5f3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73240
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>

typo3/sysext/install/Resources/Private/Templates/Upgrade/Cards.html

@@ -11,8 +11,8 @@ <h1>Upgrade</h1>
         <f:if condition="{composerMode}">
             <f:then>
                 <div class="card-footer text-muted">
-                    You can't use this feature, because your installation is in composer mode.
-                    Guide: <a href="https://docs.typo3.org/m/typo3/guide-installation/master/en-us/Upgrade/InstallTheNewSource/Index.html" target="_blank" rel="noreferrer">install the new source</a>.
+                    This function is not available as your installation is in composer mode. Please refer to the
+                    <a href="https://docs.typo3.org/upgrade" target="_blank" rel="noreferrer">TYPO3 upgrade guide</a> for more information on how to upgrade your instance.
                 </div>
             </f:then>
             <f:else>