refactor: add minor optimization improvement to day 7

Author: Flashky

src/main/java/com/adventofcode/flashk/day07/Equation.java

@@ -30,6 +30,8 @@ private boolean hasSolution(long partialResult) {
 
         if(operators.isEmpty()) {
             return partialResult == result;
+        } else if(partialResult > result) {
+            return false;
         }
 
         Integer currentOperator = operators.poll();