Update README.md (#104)

Author: Meir017

README.md

@@ -22,12 +22,6 @@ using the latest stable version:
 Install-Package FluentAssertions.Analyzers
 ```
 
-using the latest prerelease version:
-
-```powershell
-Install-Package FluentAssertions.Analyzers -IncludePrerelease -Source https://ci.appveyor.com/nuget/fluentassertions-bestpractices
-```
-
 ## Getting Started
 
 ### Build
@@ -40,4 +34,4 @@ dotnet build src
 
 ```bash
 dotnet test src --configuration Release  --filter 'TestCategory=Completed'
-```
+```