[MINOR][SPARKR] Fix SparkR regex in copy command

Fix SparkR package copy regex. The existing code leads to
```
Copying release tarballs to /home/****/public_html/spark-nightly/spark-branch-2.1-bin/spark-2.1.1-SNAPSHOT-2016_12_08_22_38-e8f351f9-bin
mput: SparkR-*: no files found
```

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

Closes #16231 from shivaram/typo-sparkr-build.

dev/create-release/release-build.sh

@@ -252,7 +252,7 @@ if [[ "$1" == "package" ]]; then
   LFTP mkdir -p $dest_dir
   LFTP mput -O $dest_dir 'spark-*'
   LFTP mput -O $dest_dir 'pyspark-*'
-  LFTP mput -O $dest_dir 'SparkR-*'
+  LFTP mput -O $dest_dir 'SparkR_*'
   # Delete /latest directory and rename new upload to /latest
   LFTP "rm -r -f $REMOTE_PARENT_DIR/latest || exit 0"
   LFTP mv $dest_dir "$REMOTE_PARENT_DIR/latest"
@@ -260,7 +260,7 @@ if [[ "$1" == "package" ]]; then
   LFTP mkdir -p $dest_dir
   LFTP mput -O $dest_dir 'spark-*'
   LFTP mput -O $dest_dir 'pyspark-*'
-  LFTP mput -O $dest_dir 'SparkR-*'
+  LFTP mput -O $dest_dir 'SparkR_*'
   exit 0
 fi