Fix whitespace

doc/src/sgml/datatype.sgml

doc/src/sgml/func.sgml

doc/src/sgml/gin.sgml

doc/src/sgml/libpq.sgml

doc/src/sgml/pgcrypto.sgml

doc/src/sgml/pgprewarm.sgml

doc/src/sgml/plpgsql.sgml

doc/src/sgml/recovery-config.sgml

doc/src/sgml/ref/alter_system.sgml

doc/src/sgml/ref/create_aggregate.sgml

doc/src/sgml/ref/create_table.sgml

doc/src/sgml/ref/pg_basebackup.sgml

doc/src/sgml/ref/psql-ref.sgml