SPARK-4365: Remove unnecessary filter call on records returned from parquet library

Since parquet library has been updated , we no longer need to filter the records returned from parquet library for null records , as now the library skips those :

from parquet-hadoop/src/main/java/parquet/hadoop/InternalParquetRecordReader.java

public boolean nextKeyValue() throws IOException, InterruptedException {
boolean recordFound = false;
while (!recordFound) {
// no more records left
if (current >= total)
{ return false; }
try {
checkRead();
currentValue = recordReader.read();
current ++; 
if (recordReader.shouldSkipCurrentRecord())
{
 // this record is being filtered via the filter2 package 
if (DEBUG) LOG.debug("skipping record");
 continue;
 }
if (currentValue == null)
{ 
// only happens with FilteredRecordReader at end of block current = totalCountLoadedSoFar;
 if (DEBUG) LOG.debug("filtered record reader reached end of block");
 continue; 
}

recordFound = true;
if (DEBUG) LOG.debug("read value: " + currentValue);
} catch (RuntimeException e)
{ throw new ParquetDecodingException(format("Can not read value at %d in block %d in file %s", current, currentBlock, file), e); }

} 
return true;
}