[BUGFIX] Remove obsolete VH usage from site template

Using <em:be.trigger triggers="{triggers}" /> in the
template seems to be obsolete since the controller
never sets the triggers variable.

This avoids a nasty cross-dependency from ext:backend
to ext:extensionmanager.

Change-Id: I0e7e452765c110b44696e3f234763f912aa9e5fc
Resolves: #98527
Releases: main
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75988


Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>