Incorrect warning for active pattern signature with generic parameters

The following signature leads to unnecessary warning (I think).

**Repro steps**

```fsharp
val (|Fst|)<'a ,'b> : a: 'a * 'b -> 'a
```

**Expected behavior**

The code should parse without warnings. (Again, I think)

**Actual behavior**

Warning: `[FS1189] Remove spaces between the type name and type parameter,
e.g. "type C<'T>", not type "C <'T>". Type parameters must be placed directly adjacent to the type name.`