Fix IgbTab child component to register parent IgbTabsModule

[Copilot]

IgbTab (child of IgbTabs) registered its own, redundant module instead of its parent's — the same anti-pattern addressed for other child-component families (e.g. IgbRatingSymbol → IgbRating, IgbCardActions → IgbCard), but missed for the Tabs family.

Change

• IgbTab.EnsureModulesLoaded now targets the parent IgbTabsModule instead of the self-referential IgbTabModule, matching the established lazy-registration convention (IgbTabsModule.Register already marks IgbTabModule as loaded internally).

protected override void EnsureModulesLoaded()
{
    if (!IgbTabsModule.IsLoadRequested(IgBlazor))
    {
        IgbTabsModule.Register(IgBlazor);
    }
}

No other files touched — IgbTabModule and IgbTabsModule themselves are unrelated to this fix.

[damyanpetev]

dupe of #357 cuz of agents outage & resend