package trigger: print build url only if there are triggered branches

[aptalca]

This PR modifies the discord notification for the package trigger so that the jenkins build url is only included if there are triggered builds. If all branches are skipped, the build url will be omitted.

Tests:

1. Synclounge master added to SKIP_PACKAGE_TRIGGER and package trigger initiated from manually updated triggertest branch
   • Action: https://github.com/linuxserver/docker-synclounge/actions/runs/11205332343
   • Discord notification: https://discord.com/channels/354974912613449730/400217715719274506/1292599616671584336
2. Synclounge master removed from SKIP_PACKAGE_TRIGGERand package trigger initiated from manually updatedtriggertest` branch
   • Action: https://github.com/linuxserver/docker-synclounge/actions/runs/11205338255
   • Discord notification: https://discord.com/channels/354974912613449730/400217715719274506/1292600054041018409

[LinuxServer-CI]

I am a bot, here are the test results for this PR:
https://ci-tests.linuxserver.io/lspipepr/jenkins-builder/077de28a-pkg-077de28a-dev-19403c7c6acb4c22d2fc7cc1522b6eb1c3e1483f-pr-291/index.html
https://ci-tests.linuxserver.io/lspipepr/jenkins-builder/077de28a-pkg-077de28a-dev-19403c7c6acb4c22d2fc7cc1522b6eb1c3e1483f-pr-291/shellcheck-result.xml

Tag	Passed
amd64-077de28a-pkg-077de28a-dev-19403c7c6acb4c22d2fc7cc1522b6eb1c3e1483f-pr-291	✅
arm64v8-077de28a-pkg-077de28a-dev-19403c7c6acb4c22d2fc7cc1522b6eb1c3e1483f-pr-291	✅