Allow for 5400 words in dump-words-to-file

After adding java.util.stream,  doc-comment-check target
started to fail due to "Too many words" while
generating out/target/common/docs/doc-comment-check-timestamp.rsp
This change extends number of dumped words to 5400.

Bug: 27692239
Change-Id: Ifa75cada7b90c5737fc7a1d10325f3a49a2238ac