The implicit_getter rule wasn't aware of the init accessor (SE-0400), causing it to incorrectly trigger on the following example

var foo: String {
  init { ... }
  get { ... } // implicit_getter violation
}

Rather than adding a check for initAccessor I updated the check to bail early unless accessorsList has a single element, that being get. This allows for forwards-compatibility if another accessor variant were to be introduced in the future. Semantically, IIUC this rule should only trigger in the aforementioned case that there's one accessor and that accessor is get — otherwise it isn't possible to elide the keyword.