[SPARK-10308] [SPARKR] Add %in% to the exported namespace

I also checked all the other functions defined in column.R, functions.R and DataFrame.R and everything else looked fine.

cc yu-iskw

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #8473 from shivaram/in-namespace.

R/pkg/NAMESPACE

@@ -47,12 +47,12 @@ exportMethods("arrange",
               "join",
               "limit",
               "merge",
+              "mutate",
+              "na.omit",
               "names",
               "ncol",
               "nrow",
               "orderBy",
-              "mutate",
-              "names",
               "persist",
               "printSchema",
               "rbind",
@@ -82,7 +82,8 @@ exportMethods("arrange",
 
 exportClasses("Column")
 
-exportMethods("abs",
+exportMethods("%in%",
+              "abs",
               "acos",
               "add_months",
               "alias",