Parser: recover on empty match clause

[auduchinok]

Adds recovery for empty match clauses like these:

match () with
|
| _ -> ()

match () with
|
| _ as _ -> ()

[github-actions[bot]]

:heavy_exclamation_mark: Release notes required

---

:white_check_mark: Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/8.0.400.md

[psfinaki]

/azp run

[azure-pipelines[bot]]

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