Razor highlighting incorrect following an `as` keyword with a Null-Coalescing Operator in a @code block.

## Issue Description ##
Syntax highlighting changes after an `as` statement with a Null-Coalescing Operator, for example `string var = e as bool ?? "";`.

## Steps to Reproduce ##
Create a new .razor file with the following contents:
```

@code {
[Parameter]
public string Param1 { get; set; }
private async Foo() {
object e = "hello";
string var = e as bool ?? "";
}
private async Bar() {

}
}
```

## Expected Behavior ##
Syntax highlighting is maintained through the whole file.

## Actual Behavior ##
The "private" and "async" keywords on `Bar`, lose syntax highlighting.

Example:

## Logs ##

### OmniSharp log ###
Post the output from Output-->OmniSharp log here

### C# log ###
Post the output from Output-->C# here

## Environment information ##

**VSCode version**: 1.76.2
**C# Extension**: 1.25.5

Mono Information
There is a problem with running OmniSharp on mono: Error: Unable to find Mono. Ensure that Mono's '/bin' folder is added to your environment's PATH variable.
Dotnet Information
.NET SDK:
Version: 7.0.101
Commit: bb24aafa11

Runtime Environment:
OS Name: Mac OS X
OS Version: 13.0
OS Platform: Darwin
RID: osx.13-arm64
Base Path: /usr/local/share/dotnet/sdk/7.0.101/

Host:
Version: 7.0.1
Architecture: arm64
Commit: 97203d38ba

.NET SDKs installed:
6.0.201 [/usr/local/share/dotnet/sdk]
6.0.402 [/usr/local/share/dotnet/sdk]
6.0.404 [/usr/local/share/dotnet/sdk]
7.0.100 [/usr/local/share/dotnet/sdk]
7.0.101 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.10 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.12 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.1 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.10 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.12 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.1 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
x64 [/usr/local/share/dotnet/x64]

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

Visual Studio Code Extensions

|Extension|Author|Version|
|---|---|---|
|blazorwasm-companion|ms-dotnettools|1.1.4|
|csharp|ms-dotnettools|1.25.5|
|godot-tools|geequlim|1.3.1|
|intellicode-api-usage-examples|VisualStudioExptTeam|0.2.7|
|jbockle-format-files|jbockle|3.4.0|
|Kotlin|mathiasfrohlich|1.7.1|
|live-server|ms-vscode|0.4.7|
|multi-file-renamer|dandidevs|1.0.0|
|remote-containers|ms-vscode-remote|0.288.0|
|remote-wsl|ms-vscode-remote|0.76.1|
|terraform|hashicorp|2.25.4|
|vscode-docker|ms-azuretools|1.24.0|
|vscode-dotnet-runtime|ms-dotnettools|1.6.0|
|vscode-tailwindcss|bradlc|0.9.11|
|vscode-xml|redhat|0.24.0|
|vscodeintellicode|VisualStudioExptTeam|1.2.30|;