Razor: "quotes" not supported in attr="@expr"

Issue Type: Bug

## Offending code
```cshtml
…
```

## In the editor
```XML
.@string.Format(FORMAT_STRING,
```

## In the compiler
```XML
.@string.Format(FORMAT_STRING, "item")
…
```

## Workaround
```cshtml
…
```

Extension version: 1.24.0
VS Code version: Code 1.63.2 (899d46d82c4c95423fb7e10e68eba52050e30ba3, 2021-12-15T09:39:46.686Z)
OS version: Linux x64 5.16.1-1-default
Restricted Mode: No

System Info

|Item|Value|
|---|---|
|CPUs|Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz (4 x 2393)|
|GPU Status|2d_canvas: enabled
gpu_compositing: enabled
multiple_raster_threads: enabled_on
oop_rasterization: disabled_off
opengl: enabled_on
rasterization: disabled_software
skia_renderer: enabled_on
video_decode: disabled_software
vulkan: disabled_off
webgl: enabled
webgl2: enabled|
|Load (avg)|1, 1, 1|
|Memory (System)|5.66GB (0.19GB free)|
|Process Argv|--crash-reporter-id 2a03cb52-9f4b-48bf-93d3-5c0537d534ee|
|Screen Reader|no|
|VM|0%|
|DESKTOP_SESSION|undefined|
|XDG_CURRENT_DESKTOP|KDE|
|XDG_SESSION_DESKTOP|undefined|
|XDG_SESSION_TYPE|x11|

A/B Experiments

```
vsliv368:30146709
vsreu685:30147344
python383:30185418
vspor879:30202332
vspor708:30202333
vspor363:30204092
pythonvspyl392:30425749
pythontb:30283811
pythonvspyt551cf:30345471
pythonptprofiler:30281270
vshan820:30294714
vstes263:30335439
pythondataviewer:30285071
vscod805:30301674
pythonvspyt200:30340761
binariesv615:30325510
bridge0708:30335490
bridge0723:30353136
vsaa593cf:30376535
vsc1dst:30428979
pythonvs932:30410667
vscop804cf:30404767
vscop940:30404999
vsrem710:30416614
vsbas813:30426126

```