Fix SAT warnings (#14202)

* Fix SAT warnings

- checkstyle.ModifierOrderCheck
- checkstyle.OneStatementPerLineCheck
- checkstyle.NeedBracesCheck
- PMD.UseStandardCharsets
- PMD.UseCollectionIsEmpty
- PMD.UnusedLocalVariable
- PMD.SimplifyBooleanReturns where reasonable, suppress where
readability is better without change
- PMD.SimplifyBooleanExpressions

* Include StandardCharsets

Signed-off-by: Holger Friedrich <mail@holger-friedrich.de>

bundles/org.openhab.binding.millheat/src/main/java/org/openhab/binding/millheat/internal/handler/MillheatAccountHandler.java

@@ -128,10 +128,7 @@ public class MillheatAccountHandler extends BaseBridgeHandler {
 
     private boolean allowModelUpdate() {
         final long timeSinceLastUpdate = System.currentTimeMillis() - model.getLastUpdated();
-        if (timeSinceLastUpdate > MIN_TIME_BETWEEEN_MODEL_UPDATES_MS) {
-            return true;
-        }
-        return false;
+        return timeSinceLastUpdate > MIN_TIME_BETWEEEN_MODEL_UPDATES_MS;
     }
 
     public MillheatModel getModel() {