[SPARKR][EXAMPLE] change example APP name

## What changes were proposed in this pull request?

(Please fill in changes proposed in this fix)

For R SQL example, appname is "MyApp". While examples in scala, Java and python, the appName is "x Spark SQL basic example".

I made the R example consistent with other examples.

## How was this patch tested?

(Please explain how this patch was tested. E.g. unit tests, integration tests, manual tests)

Manual test
(If this patch involves UI changes, please attach a screenshot; otherwise, remove this)

Author: wm624@hotmail.com <wm624@hotmail.com>

Closes #14703 from wangmiao1981/example.

examples/src/main/r/RSparkSQLExample.R

@@ -18,7 +18,7 @@
 library(SparkR)
 
 # $example on:init_session$
-sparkR.session(appName = "MyApp", sparkConfig = list(spark.some.config.option = "some-value"))
+sparkR.session(appName = "R Spark SQL basic example", sparkConfig = list(spark.some.config.option = "some-value"))
 # $example off:init_session$