triple-slash docs accidentally merged when put in the wrong position

[kubukoz]

When you do this:

$version: "2"

namespace demo

structure Hello {
    @required
    /// totally a string
    s: String
    /// a number!
    i: Integer
}

The result will end up concatenating both doc strings and putting them on i:

{
    "smithy": "2.0",
    "shapes": {
        "demo#Hello": {
            "type": "structure",
            "members": {
                "s": {
                    "target": "smithy.api#String",
                    "traits": {
                        "smithy.api#required": {}
                    }
                },
                "i": {
                    "target": "smithy.api#Integer",
                    "traits": {
                        "smithy.api#documentation": "totally a string\na number!"
                    }
                }
            }
        }
    }
}

whereas if i has no /// on it, you'll rightfully get a warning about the wrong position:

I think the actual behavior in the original snippet should be:

• produce the same type of warning as in the screenshot
• don't concat the docs (ignore the comment from totally a string completely)