Documentation spelling mistake REMOVE_DUPLICATE -> REMOVE_DUPLICATES

[mmterpstra]

Minor spelling mistake in docs?

Affecting current version and documentation on the gatk page. (3.4.0)

REMOVE_DUPLICATE should be changed to REMOVE_DUPLICATES in the line below.

picard/src/main/java/picard/sam/markduplicates/MarkDuplicates.java

Line 98 in fc0b084

"<p>If desired, duplicates can be removed using the REMOVE_DUPLICATE and REMOVE_SEQUENCING_DUPLICATES options.</p>" +

Also thanks for maintaining the software.