Code blocks expressions may be incorrectly merged and formatted as a single one

elm-format version: 0.8.2

When running `elm-format` once on the following top-level comment with two expression examples in a code block:
```
{-|

1 == 1
(-2 == 3)

-}
```
We get:
```
{-|

1 == 1

-2 == 3

-}
```
But when running `elm-format` again, we get:
```
{-|

1
== 1
- 2
== 3

-}
```

This is most likely not an expected result.

Start by reproducing the example with elm-format 0.8.2 and running the formatter twice, comparing how the two expressions in the top-level comment code block change. Inspect the formatting path for comment code blocks; done means repeated formatting is stable and the two examples remain separate.

Written by the indexing model from the issue text.