Doc comment has trailing space

**TypeScript Version:**  master

**Code**

```ts
/// <reference path='fourslash.ts'/>

// @Filename: quickInfoJsDocTags.ts
/////** Doc */
////const /**/x = 0;

verify.quickInfoAt("", "const x: 0", "Doc");
```

**Expected behavior:**

Test passes.

**Actual behavior:**

Test fails. Doc comment is actually `"Doc "`.