Fixed interval tag

public/biopet-extensions/src/main/scala/nl/lumc/sasc/biopet/extensions/gatk/Gatk.scala

@@ -68,7 +68,7 @@ abstract class Gatk extends BiopetJavaCommandLineFunction with Reference with Ve
     required("-R", reference) +
     optional("-K", gatkKey) +
     optional("-et", et) +
-    repeat("-I", intervals) +
+    repeat("-L", intervals) +
     repeat("-XL", excludeIntervals) +
     repeat("-ped", pedigree)
 }
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