Summary: Fixes mismatch in wails version between `go.mod` and `go.sum`.
Fixes the following issue with vendoring mods:

Before:

```
$ go mod vendor && echo success
go: github.com/wailsapp/[email protected]: missing go.sum entry for go.mod file; to add it:
        go mod download github.com/wailsapp/wails
```

After:

```
$ go mod vendor && echo success
success
```