Table with no primary key seems to cause an out of memory error during schema migration

I'm getting the following error in what appears to be one of either `verifySchema` or `autoMigrate`.

```
internal error: Unable to commit 1048576 bytes of memory
(GHC version 8.6.5 for x86_64_unknown_linux)
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
```

We ended up finding that the problem seems to be related to having a table with no primary key. The `Table` instance was defined like this.

```
instance Table FooT where
data PrimaryKey FooT f = FooNoId
deriving stock (Generic)
deriving anyclass (Beamable)
primaryKey _ = FooNoId
```

But when we changed it to have a primary key, the above memory crash went away. I don't have time to dig into the details at the moment, but I wanted to record this behavior in case anyone else runs into it.