pgsql: Remove unused nbtree array advancement variable.

Remove unused nbtree array advancement variable. Remove a variable that is no longer in use following commit 9a2e2a28. It's not immediately clear why there were no compiler warnings about this oversight. Author: Peter Geoghegan Backpatch-through: 18 Branch -- REL_18_STABLE Details ---

pgsql: Remove unused nbtree array advancement variable.

Remove unused nbtree array advancement variable. Remove a variable that is no longer in use following commit 9a2e2a28. It's not immediately clear why there were no compiler warnings about this oversight. Author: Peter Geoghegan Backpatch-through: 18 Branch -- master Details --- https:/