[SPARK-25795][R][EXAMPLE] Fix CSV SparkR SQL Example

## What changes were proposed in this pull request?

This PR aims to fix the following SparkR example in Spark 2.3.0 ~ 2.4.0.

```r
> df <- read.df("examples/src/main/resources/people.csv", "csv")
> namesAndAges <- select(df, "name", "age")
...
Caused by: org.apache.spark.sql.AnalysisException: cannot resolve '`name`' given input columns: [_c0];;
'Project ['name, 'age]
+- AnalysisBarrier
      +- Relation[_c0#97] csv
```

- https://dist.apache.org/repos/dist/dev/spark/v2.4.0-rc3-docs/_site/sql-programming-guide.html#manually-specifying-options
- http://spark.apache.org/docs/2.3.2/sql-programming-guide.html#manually-specifying-options
- http://spark.apache.org/docs/2.3.1/sql-programming-guide.html#manually-specifying-options
- http://spark.apache.org/docs/2.3.0/sql-programming-guide.html#manually-specifying-options

## How was this patch tested?

Manual test in SparkR. (Please note that `RSparkSQLExample.R` fails at the last JDBC example)

```r
> df <- read.df("examples/src/main/resources/people.csv", "csv", sep=";", inferSchema=T, header=T)
> namesAndAges <- select(df, "name", "age")
```

Closes #22791 from dongjoon-hyun/SPARK-25795.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

examples/src/main/r/RSparkSQLExample.R

@@ -114,7 +114,7 @@ write.df(namesAndAges, "namesAndAges.parquet", "parquet")
 
 
 # $example on:manual_load_options_csv$
-df <- read.df("examples/src/main/resources/people.csv", "csv")
+df <- read.df("examples/src/main/resources/people.csv", "csv", sep=";", inferSchema=T, header=T)
 namesAndAges <- select(df, "name", "age")
 # $example off:manual_load_options_csv$