Fix stub exception message in two-bucket

The stub exception message for getResult was incorrectly asking students
to implement the constructor rather than the getResult method. This
commit changes the stub messages to use the more recent format.

[no important files changed]

Author: kahgoh

exercises/practice/two-bucket/src/main/java/TwoBucket.java

@@ -1,11 +1,11 @@
 class TwoBucket {
 
     TwoBucket(int bucketOneCap, int bucketTwoCap, int desiredLiters, String startBucket) {
-        throw new UnsupportedOperationException("Please implement the TwoBucket(int, int, int, String) constructor.");
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }
 
     Result getResult() {
-        throw new UnsupportedOperationException("Please implement the TwoBucket(int, int, int, String) constructor.");
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
     }
 
 }