Update Impala website to reduce emphasis on Hadoop

The Impala website at ASF https://impala.apache.org/  is the first hit returned for “Apache Impala”. 

Update the first line of the description to say ="Apache Impala is a modern, open source, distributed SQL query engine for open data formats."

instead of "Apache Impala is a modern, open source, distributed SQL query engine for Apache Hadoop."

Also mention Ranger instead of Sentry, and add references to Iceberg.