PostgreSQL reverts SQL/PGQ property graph queries out of version 19

Sources: primary, discussion
Summary: A commit on the PostgreSQL 19 branch, authored by Peter Eisentraut on 2026-09-07, reverts the SQL/PGQ property graph work. The revert removes CREATE PROPERTY GRAPH, the GRAPH_TABLE query clause, and the pg_propgraph catalogs from the branch.
Why it matters: SQL/PGQ is out of version 19 before general availability, so anyone who planned on GRAPH_TABLE, CREATE PROPERTY GRAPH, or the pg_propgraph catalogs in 19 has to replan.