## What changes were proposed in this pull request?

Since [SPARK-15639](https://github.com/apache/spark/pull/13701), `spark.sql.parquet.cacheMetadata` and `PARQUET_CACHE_METADATA` is not used. This PR removes from SQLConf and docs.

## How was this patch tested?

Pass the existing Jenkins.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #19129 from dongjoon-hyun/SPARK-13656.