[DOCS] Fix AbstractDiffable typo (#59034) (#63669)

Co-authored-by: Howard <[email protected]>

Author: jrodewig

server/src/main/java/org/elasticsearch/cluster/AbstractDiffable.java

@@ -27,7 +27,7 @@
 
 /**
  * Abstract diffable object with simple diffs implementation that sends the entire object if object has changed or
- * nothing is object remained the same.
+ * nothing if object remained the same.
  */
 public abstract class AbstractDiffable<T extends Diffable<T>> implements Diffable<T> {