can not format c# code after C# installed

## Environment data
`dotnet --info` output:
版本: 1.46.1 (system setup)
提交: cd9ea6488829f560dc949a8b2fb789f3cdc05f5d
日期: 2020-06-17T21:13:20.174Z
Electron: 7.3.1
Chrome: 78.0.3904.130
Node.js: 12.8.1
V8: 7.8.279.23-electron.0
OS: Windows_NT x64 10.0.14393
C# Extension version: v1.22.1

## OmniSharp log

## Steps to reproduce
open a `.cs` file, not a `workspace`,and then `alt+shift+f`,

## Expected behavior
format well
## Actual behavior
shows that no format tool installed.