Language service panic for fail in loop

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**Describe the bug**

```qsharp
@EntryPoint(Adaptive)
operation Main() : Int {
repeat {
fail "hello"
} until 1 < 2
}
```
```
[wasm] Wasm panic occurred: panicked at source/compiler/qsc_fir_transforms/src/invariants.rs:707:5:
Non-Unit block-tail invariant violation: callable 'Main' body Block 0 has type Prim(Int) but trailing Expr 3 has type Tuple([])
```
```
[wasm] Wasm panic occurred: panicked at source/language_service/src/lib.rs:309:44:
RefCell already mutably borrowed
```

**To Reproduce**

[Playground](https://microsoft.github.io/qdk/?code=H4sIAAAAAAAACnNwzSspqgzIz8wr0XBMSSwoySxL1eTKL0gtSizJzM9T8E3MzNPQVLBS8MwrUajmUlBQUChKLUhNhHFAIC0xM0dBKSM1JydfCSxYq1CaV5KZo2CoYKNgxFULADBsJ95kAAAA)

Reproduce the Q# example in the linked Playground, then inspect source/compiler/qsc_fir_transforms/src/invariants.rs around line 707 and source/language_service/src/lib.rs around line 309. Trace how the fail inside the repeat loop produces the invalid block-tail type and the subsequent borrow panic. Done means the example no longer causes either WASM panic and reports or handles the code normally.

Written by the indexing model from the issue text.