Documentation: fuzzy query's max_expansion fix

See line org.elasticsearch.index.query.FuzzyQueryParser:70
```java
  int maxExpansions = FuzzyQuery.defaultMaxExpansions;
```

The contents of org.apache.lucene.search.FuzzyQuery
```java
  public final static int defaultPrefixLength = 0;
  public final static int defaultMaxExpansions = 50;
```