Correct VARIANT Logical Type annotation in Parquet examples

[alamb]

Rationale for this change

• @wgtmac pointed out in [BLOG] Variant Type in Apache Parquet for Semi-Structured Data parquet-site#171 (comment)

That the example of the VARAINT type annotation in this repository did not have an integer field

I double checked and the VARAINT logical type does indeed have a integer field ("specification_version"):

parquet-format/src/main/thrift/parquet.thrift

Lines 409 to 413 in 38818fa

	struct VariantType {
	// The version of the variant specification that the variant was
	// written with.
	1: optional i8 specification_version
	}

This is also consistent with the parquet-java tests:

https://github.com/apache/parquet-java/blob/7148464a6b1a795f0058a811de2215d111b976ce/parquet-avro/src/test/java/org/apache/parquet/avro/TestReadVariant.java#L295

https://github.com/apache/parquet-java/blob/7148464a6b1a795f0058a811de2215d111b976ce/parquet-column/src/test/java/org/apache/parquet/parser/TestParquetParser.java#L455

What changes are included in this PR?

Updated the representation of unshredded and shredded Variants in the example to include the variant version

Do these changes have PoC implementations?

No this does not change the spec at all, just the examples

[wgtmac]

Thanks for a quick fix!