EAMxx: fix docs mentioning timestamp usage within an atm proc

Author: bartgol

components/eamxx/docs/_presentations_srcs/eamxx-tutorial-2025-part2.md

@@ -487,7 +487,7 @@ void POMPEI::run_impl(const double dt) {
   using PC = scream::physics::Constants<Real>;
   auto g   = PC::gravit;
 
-  auto t    = timestamp() + dt;
+  auto t    = end_of_step_ts();
   auto rate = pompei::ash_emission_rate(t.days_from(m_eruption_start));
   auto mass = dt * rate;
 

components/eamxx/docs/developer/dev_testing/testing_for_development.md

@@ -76,7 +76,7 @@ be the `eamxx_inject_ash_process_interface.<x>pp` files, located at
       [...] // set source_mask=1 only on area of interest, using lat/lon field
     }
     void MAM_AshInjection::run_impl(const double dt) {
-      auto t = this->timestamp() + dt; // timestamp() is the START of step time
+      auto t = end_of_step_ts();
       auto ash = get_field_out("ash");
       auto rate = compute_ash_injection_rate(
           t); // defined in ash_source_calculation.hpp header