test/tmm: fix thresholdAbove255_clamps loop count

The unknown counter is a 6-bit field (saturates at 63); the threshold is
capped at 60 so saturated readings always exceed it. A config value of 300
clamps to 60, meaning the 61st packet is the first drop — not the 256th.
Loop count corrected from 255 to 60 to match the actual implementation cap.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: NomDeTom

test/test_traffic_management/test_main.cpp

@@ -1006,8 +1006,9 @@ static void test_tm_unknownPackets_resetAfterWindowExpires(void)
 }
 
 /**
- * Verify unknown threshold values above 255 clamp to the counter ceiling.
- * Important to align config semantics with saturating counter storage.
+ * Verify unknown threshold values above the implementation cap (60) are clamped.
+ * The counter is a 6-bit field (saturates at 63); threshold is capped at 60 so a
+ * saturated reading always exceeds it. A config value of 300 should behave as 60.
  */
 static void test_tm_unknownPackets_thresholdAbove255_clamps(void)
 {
@@ -1016,7 +1017,7 @@ static void test_tm_unknownPackets_thresholdAbove255_clamps(void)
     TrafficManagementModuleTestShim module;
     meshtastic_MeshPacket packet = makeUnknownPacket(kRemoteNode);
 
-    for (int i = 0; i < 255; i++) {
+    for (int i = 0; i < 60; i++) {
         ProcessMessage result = module.handleReceived(packet);
         TEST_ASSERT_EQUAL_INT(static_cast<int>(ProcessMessage::CONTINUE), static_cast<int>(result));
     }