HPCC-12038 Clarify Contributor to doc

Signed-off-by: Jim DeFabia <jamesdefabia@lexisnexis.com>
Merge pull request #6313 from JamesDeFabia/12038ClarifyPGContributor

HPCC-12038 Clarify Contributor to doc

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>