template0 is having high age of datforzenxid

Hi,

I am running Postgresql 10 where I can see the template0 database is having
longest datfrozenxid:
```db_name age_of_datfrozenxid
--------------------------------------
postgres 251365
template1 234574
template0 75366462
db1 253097
db2 250649
db3 250649
db4 14641
db5 14214```

Initially I had high age for all the databases and I ran "vacuum freeze"
which brought down the age of other databases. But how can I do the same
for template0?
Please advise.

Thanks.