activitymonitor: remove B_MAX_CPU_COUNT reference

It has no use, since we don't know its value and the list of colors
might be longer (for example, for ARM currently B_MAX_CPU_COUNT is
only 1). The modula operator later on makes sure we keep within the
bounds of the kColors array anyway.

src/apps/activitymonitor/DataSource.cpp

@@ -949,7 +949,7 @@ CPUUsageDataSource::_SetCPU(int32 cpu)
 
 	fLabel << " " << B_TRANSLATE("usage");
 
-	const rgb_color kColors[B_MAX_CPU_COUNT] = {
+	const rgb_color kColors[] = {
 		// TODO: find some better defaults...
 		{200, 0, 200},
 		{0, 200, 200},