Implicit binding of inputs is allowed in 1.0 docs

[a-frantz]

This goes against the spec, which says implicit bindings are only allowed in >=v1.1.

Discovered in #244

Confirmed by this test:

$ cat tmp.wdl
version 1.0

workflow test {
    input {
        String foo
    }

    call bar { input: foo }
}

task bar {
    input {
        String foo
    }

    command <<<>>>
}
$ sprocket check tmp.wdl
warning[UnusedCall]: unused call `bar`
  ┌─ tmp.wdl:8:10
  │
8 │     call bar { input: foo }
  │          ^^^

warning[UnusedInput]: unused input `foo`
   ┌─ tmp.wdl:13:16
   │
13 │         String foo
   │                ^^^