[MINOR][R] Fix R lint failure

## What changes were proposed in this pull request?

The lint failure bugged me:

```R
R/SQLContext.R:715:97: style: Trailing whitespace is superfluous.
#'        file-based streaming data source. \code{timeZone} to indicate a timezone to be used to
                                                                                                ^
tests/fulltests/test_streaming.R:239:45: style: Commas should always have a space after.
  expect_equal(times[order(times$eventTime),][1, 2], 2)
                                            ^
lintr checks failed.
```

and I actually saw https://amplab.cs.berkeley.edu/jenkins/job/spark-master-test-sbt-hadoop-2.6-ubuntu-test/500/console too. If I understood correctly, there is a try about moving to Unbuntu one.

## How was this patch tested?

Manually tested by `./dev/lint-r`:

```
...
lintr checks passed.
```

Author: hyukjinkwon <[email protected]>

Closes #20879 from HyukjinKwon/minor-r-lint.

(cherry picked from commit 92e9525)
Signed-off-by: hyukjinkwon <[email protected]>

R/pkg/R/SQLContext.R

@@ -727,7 +727,7 @@ read.jdbc <- function(url, tableName,
 #' @param schema The data schema defined in structType or a DDL-formatted string, this is
 #'               required for file-based streaming data source
 #' @param ... additional external data source specific named options, for instance \code{path} for
-#'        file-based streaming data source. \code{timeZone} to indicate a timezone to be used to 
+#'        file-based streaming data source. \code{timeZone} to indicate a timezone to be used to
 #'        parse timestamps in the JSON/CSV data sources or partition values; If it isn't set, it
 #'        uses the default value, session local timezone.
 #' @return SparkDataFrame

R/pkg/tests/fulltests/test_streaming.R

@@ -236,7 +236,7 @@ test_that("Watermark", {
 
   times <- collect(sql("SELECT * FROM times"))
   # looks like write timing can affect the first bucket; but it should be t
-  expect_equal(times[order(times$eventTime),][1, 2], 2)
+  expect_equal(times[order(times$eventTime), ][1, 2], 2)
 
   stopQuery(q)
   unlink(parquetPath)