fix(buzz): use assertTrue instead of assert in ForumCommentEventTest

Kotlin/Native marks the stdlib `assert()` with `@ExperimentalNativeApi`, so
the iOS test target (`compileTestKotlinIosSimulatorArm64`) failed to compile
without an opt-in — while JVM/Android were fine. Swap it for `assertTrue`
from `kotlin.test`, which needs no opt-in on any target and matches the
assertions already used in this file.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J8KBSw6smQRyXLiWHeDsZ8

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/buzz/forum/ForumCommentEventTest.kt

@@ -23,6 +23,7 @@ package com.vitorpamplona.quartz.buzz.forum
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertNull
+import kotlin.test.assertTrue
 
 class ForumCommentEventTest {
     private val channel = "3f2504e0-4f89-41d3-9a0c-0305e82c3301"
@@ -70,6 +71,6 @@ class ForumCommentEventTest {
         ev: ForumCommentEvent,
         expected: Array<String>,
     ) {
-        assert(ev.tags.any { it.toList() == expected.toList() }) { "missing tag ${expected.toList()}" }
+        assertTrue(ev.tags.any { it.toList() == expected.toList() }, "missing tag ${expected.toList()}")
     }
 }