Added warning re validatorStatuses cache

ethereum/spec/src/main/java/tech/pegasys/teku/spec/logic/common/statetransition/epoch/AbstractEpochProcessor.java

@@ -104,6 +104,16 @@ public BeaconState processEpoch(final BeaconState preState) throws EpochProcessi
 
   protected void processEpoch(final BeaconState preState, final MutableBeaconState state)
       throws EpochProcessingException {
+    /*
+      WARNING: After Electra, it is possible that the validator set is updated within epoch processing
+      (process_pending_deposits). This means that the validator set in the state can get out of sync with
+      our validatorStatuses cache. This is not a problem for the current epoch processing, but it can cause
+      undesired side effects in the future.
+
+      Up until Electra, the only function that uses validatorStatuses after process_pending_deposits is
+      process_effective_balance_updates, and in this particular case it is ok that we don't have the new validators
+      in validatorStatuses.
+     */
     final ValidatorStatuses validatorStatuses =
         validatorStatusFactory.createValidatorStatuses(preState);