Doc changes for new nested JSON reader [skip ci]

[res-life]

Contributes to #7518
Signed-off-by: Chong Gao [email protected]

Changes:

• Cause error on invalid data
• Remove the desc of does not support column pruning.

The following shows it supports column pruning now:

$ cat /tmp/people.json
{"name":"Michael"}
{"name":"Andy", "age":30}
{"name":"Justin", "age":19}

scala> import org.apache.spark.sql.types._
scala> spark.conf.set("spark.rapids.sql.format.json.read.enabled", "true")
scala> spark.conf.set("spark.rapids.sql.format.json.enabled", "true")
scala> val schema = StructType(Seq(StructField("name", StringType)))    // Only specify one column
scala> val df = spark.read.schema(schema).json("/tmp/people.json")
scala> df.show()
23/02/20 10:17:36 WARN GpuOverrides: 
!Exec <CollectLimitExec> cannot run on GPU because the Exec CollectLimitExec has been disabled, and is disabled by default because Collect Limit replacement can be slower on the GPU, if huge number of rows in a batch it could help by limiting the number of rows transferred from GPU to CPU. Set spark.rapids.sql.exec.CollectLimitExec to true if you wish to enable it
  @Partitioning <SinglePartition$> could run on GPU
  *Exec <FileSourceScanExec> will run on GPU

+-------+
|   name|
+-------+
|Michael|
|   Andy|
| Justin|
+-------+

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build

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Updated, thanks ttnghia.

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build