A possible typo in GRANDPA paper

A possible typo in the GRANDPA paper, page 7, line 6. I check the `.tex` source file, it looks like:

```tex
given by the last block in the chain with head $g(V_{r,v})$ for which it is possible for $C_{r,r}$ to have a supermajority.
```

I figure it should be:

```tex
it is possible for $C_{r,v}$ to have a supermajority
```