Minor typo in IndexReader and CompositeReader javadoc for trunk

[Jack Krupansky]

Minor typo in the javadoc for IndexReader.java and CompositeReader.java:

<code>DirectoryReader,open()</code>

(note the comma)
s.b.

<code>DirectoryReader.open()</code>

(Although some may prefer “#” rather than “.”)

-- Jack Krupansky