As of 1.0, the first infix operator is an identifier

I've been going through more of the JuliaSyntax v1.0 changes for JuliaSyntaxHighlighting, and I've come across one that seems like it could be a bug. In v0.4.10 I see this:

```
julia> parseall(GreenNode, "x + y + z")
1:9 │[toplevel]
1:9 │ [call]
1:1 │ Identifier ✔
2:2 │ Whitespace
3:3 │ + ✔
4:4 │ Whitespace
5:5 │ Identifier ✔
6:6 │ Whitespace
7:7 │ +
8:8 │ Whitespace
9:9 │ Identifier ✔
```

While in 1.0.2 I see:

```
julia> parseall(GreenNode, "x + y + z")
1:9 │[toplevel]
1:9 │ [call]
1:1 │ Identifier ✔
2:2 │ Whitespace
3:3 │ Identifier ✔
4:4 │ Whitespace
5:5 │ Identifier ✔
6:6 │ Whitespace
7:7 │ +
8:8 │ Whitespace
9:9 │ Identifier ✔
```

The first `+` is now a `K"Identifier"` not a `K"+"`.