Remove leftover function prototype.
Remove leftover function prototype.

The prototype for inval_twophase_postcommit wasn't removed when it's definition
was removed in efc16ea520679d713d98a2c7bf1453c4ff7b91ec / the initial HS commit.

Andres Freund

zeroae/postgres-xl,oberstet/postgres-xl,greenplum-db/gpdb,oberstet/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,yazun/postgres-xl,50wu/gpdb,zeroae/postgres-xl,ashwinstar/gpdb,jmcatamney/gpdb,Postgres-XL/Postgres-XL,lisakowen/gpdb,50wu/gpdb,yazun/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,adam8157/gpdb,ovr/postgres-xl,ovr/postgres-xl,adam8157/gpdb,techdragon/Postgres-XL,50wu/gpdb,jmcatamney/gpdb,50wu/gpdb,yazun/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,oberstet/postgres-xl,yazun/postgres-xl,jmcatamney/gpdb,xinzweb/gpdb,lisakowen/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,techdragon/Postgres-XL,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,pavanvd/postgres-xl,greenplum-db/gpdb,techdragon/Postgres-XL,50wu/gpdb,adam8157/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,xinzweb/gpdb,xinzweb/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,lisakowen/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,lisakowen/gpdb,yazun/postgres-xl,ovr/postgres-xl,adam8157/gpdb,zeroae/postgres-xl,jmcatamney/gpdb,techdragon/Postgres-XL,50wu/gpdb,pavanvd/postgres-xl,adam8157/gpdb,greenplum-db/gpdb,ovr/postgres-xl,xinzweb/gpdb,pavanvd/postgres-xl,Postgres-XL/Postgres-XL,ashwinstar/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,Postgres-XL/Postgres-XL,ovr/postgres-xl,xinzweb/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,adam8157/gpdb,jmcatamney/gpdb,lisakowen/gpdb,oberstet/postgres-xl,ashwinstar/gpdb,Postgres-XL/Postgres-XL,50wu/gpdb,xinzweb/gpdb,oberstet/postgres-xl