Allow the offside rule for attributes

The following code doesn't compile:

```fsharp

[]

type T =
class end

```

You need to supply the semicolon:

```fsharp

[]

type T =
class end

```

## Pros and Cons

The advantages of making this adjustment to F# are:

* Consistency with lists, arrays, sequences

The disadvantages of making this adjustment to F# are:

* None

## Extra information

Estimated cost (XS, S, M, L, XL, XXL): S

Related suggestions: https://github.com/dotnet/fsharp/issues/7752

## Affidavit (please submit!)

Please tick this by placing a cross in the box:
* [x] This is not a question (e.g. like one you might ask on [stackoverflow](http://stackoverflow.com)) and I have searched stackoverflow for discussions of this issue
* [x] I have [searched both open and closed suggestions on this site](http://github.com/fsharp/fslang-suggestions/issues) and believe this is not a duplicate
* [x] This is not something which has obviously "already been decided" in previous versions of F#. If you're questioning a fundamental design decision that has obviously already been taken (e.g. "Make F# untyped") then please don't submit it.

Please tick all that apply:
* [x] This is not a breaking change to the F# language design
* [x] I or my company would be willing to help implement and/or test this