ci: Stop running server pipelines for the lts branch

[alexvy86]

Description

Server releases will never be made from the LTS branch, so having the pipelines trigger for PRs to it / commits in it is not necessary. Arguably, we could remove the whole server/ folder in LTS, but I did not try to be that aggressive with this PR.

This just makes it so:

• Those pipelines don't run for the lts branch.
• The long-gone next branch is removed from the triggers section
• Pipelines that used to run for PRs into release/* branches but not on commits to those branches (historian, gitrest, gitssh), now also run for commits on the branches. The routerlicious pipeline already behaves like this. Not clear why we wouldn't want the others to do the same.

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[Copilot]

Pull request overview

This PR updates Azure Pipelines trigger configuration for the server pipelines so they no longer run for the lts branch (and removes the obsolete next branch), aligning CI behavior with the fact that server releases aren’t produced from LTS. It also makes historian/gitrest/gitssh pipelines run on direct commits to release/* branches (not just PRs targeting them), consistent with the routerlicious pipeline behavior.

Changes:

• Removed lts and next from CI/PR triggers for the server pipelines.
• Enabled commit triggers on release/* branches for historian, gitrest, and gitssh pipelines.
• Kept routerlicious behavior consistent while removing obsolete branch triggers.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tools/pipelines/server-routerlicious.yml	Removes next and lts from trigger/pr branch includes; keeps release/* behavior unchanged.
tools/pipelines/server-historian.yml	Removes next/lts from triggers and adds commit triggering on release/*.
tools/pipelines/server-gitssh.yml	Removes next/lts from triggers and adds commit triggering on release/*.
tools/pipelines/server-gitrest.yml	Removes next/lts from triggers and adds commit triggering on release/*.

[ChumpChief]

Seems good to me, would you also merge this to the lts branch?