Fix ClassDAreTeammates config being ignored for Class-D friendly fire

[dualfroz]

Problem

Repo: Vretu-Dev/UsefulHints
Base: main
Head: dualfroz:fix/classd-teammates-friendly-fire
No tracking issue (behaviour bug found while reading the source; nothing to Closes).

---

The ClassDAreTeammates option currently has no effect. In FFWarning.OnHurting
the if branch that gated the warning on Config.ClassDAreTeammates and its else
branch were identical:

if (ev.Attacker.Role.Team == Team.ClassD && ev.Player.Role.Team == Team.ClassD && Config.ClassDAreTeammates)
{
    ev.Attacker.ShowHint(string.Format(Config.FriendlyFireWarning), 1);
    ev.Player.ShowHint(string.Format(Config.DamageTakenWarning, ev.Attacker.Nickname), 2);
}
else
{
    ev.Attacker.ShowHint(string.Format(Config.FriendlyFireWarning), 1);
    ev.Player.ShowHint(string.Format(Config.DamageTakenWarning, ev.Attacker.Nickname), 2);
}

Both paths showed the warning, so setting ClassDAreTeammates: false still fired the
friendly-fire warning when one Class-D hurt another.

This collapses the duplicated branches into a single guarded block, so the warning is
skipped only for the intended case: two Class-D players hurting each other while
ClassDAreTeammates is false. Every other same-side pairing (MTF, Chaos, etc.) is
unchanged.

Root cause: UsefulHints/EventHandlers/Modules/FFWarning.cs, lines 28-38 (parent
commit 3c4e6b0), inside FFWarning.OnHurting.

Flags

SECURITY.md found in this repository; README.md has no AI-disclosure or
CLA/DCO language either. No policy gate applies.

• No open upstream PR or issue covers this bug (checked
  pulls?state=open&per_page=100 and all issues, all-time, on
  Vretu-Dev/UsefulHints).

Limitations

• Full project build not verified in this environment (see Verification above);
  only the isolated boolean-logic extraction was run.
• No automated test suite exists in the repository to regression-guard this fix.

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