Would help if you provide example rust code

Sorry, here a simple example

```
async fn main() -> Result<(), dyn std::error::Error> {
    std::thread::sleep(std::time::Duration::from_secs(2))
}
```

I get 
```
[rustc] (E0308) mismatched types
expected enum Result&lt;(), (dyn std::error::Error + 'static)&gt;
found unit type ()
[main.rs:1] expected Result&lt;(), (dyn std::error::Error + 'static)&gt; because of return type
[main.rs:2] try adding an expression at the end of the block: ;   Ok(())
```

I tried removing the async keyword, and the tooltip displays correctly then.
```
[rust-analyzer] (E0308) expected Result<(), dyn Error>, found ()
```

I have tried multiple times but I can't see a broken tooltip. I only see the following tooltip and a different one which shows the description of symbol under cursor along with the error below

```
[rust-analyzer] (E0308) expected Result<(), dyn Error>, found ()
```

---

My rust analyzer version is:
```
rust-analyzer --version
rust-analyzer 1.71.0 (8ede3aa 2023-07-12)
```

Sorry this is the tooltip I see:
```
[rust-analyzer] (type-mismatch) expected Result<(), dyn Error>, found ()
```

Created attachment 162124 [details]
rustin

Created attachment 162125 [details]
rustout

Maybe something to do with locales?
```
$ rust-analyzer --version && kate --version && env | grep 'LC_*'
rust-analyzer 1.74.0-nightly (65ea825 2023-09-18)
QSocketNotifier: Can only be used with threads started with QThread
kate 23.08.1
LC_ADDRESS=fr_FR.UTF-8
LC_NAME=fr_FR.UTF-8
LC_MONETARY=fr_FR.UTF-8
LC_PAPER=fr_FR.UTF-8
LC_IDENTIFICATION=en_US.UTF-8
LC_RESPONSE=POSIX
LC_TELEPHONE=fr_FR.UTF-8
LC_MESSAGES=POSIX
LC_MEASUREMENT=fr_FR.UTF-8
LC_CTYPE=en_US.UTF-8
LC_TIME=fr_FR.UTF-8
LC_COLLATE=en_US.UTF-8
LC_NUMERIC=fr_FR.UTF-8
```

I changed LSP to be script that does the following
```
tee /tmp/lsp/rustin | rustup run nightly rust-analyzer "$@" | tee /tmp/lsp/rustout
```
loaded the file containing the example code and displayed the tooltip (which displayed incorrectly).
rustin and rustout are provided in attachments

Reproduced after upgrading rust-analyzer

Git commit b20feef77ca830684ce8570e59e63830791c28a5 by Waqar Ahmed.
Committed on 10/10/2023 at 08:51.
Pushed by waqar into branch 'master'.

Use plainText for diagnostic tooltip

M  +2    -2    apps/lib/diagnostics/diagnosticview.cpp

https://invent.kde.org/utilities/kate/-/commit/b20feef77ca830684ce8570e59e63830791c28a5