chore: cleanup dead code (#271)

Author: Meir017

src/FluentAssertions.Analyzers/Utilities/ArgumentValidator.cs

@@ -122,13 +122,4 @@ private Diagnostic AnalyzeExpressionSafely(ExpressionSyntax expression, Semantic
 
 public abstract class FluentAssertionsAnalyzer : FluentAssertionsAnalyzer<FluentAssertionsCSharpSyntaxVisitor>
 {
-}
-
-public abstract class TestingLibraryAnalyzerBase : FluentAssertionsAnalyzer
-{
-    protected abstract string TestingLibraryModule { get; }
-    protected abstract string TestingLibraryAssertionType { get; }
-
-    protected override bool ShouldAnalyzeVariableNamedType(INamedTypeSymbol type, SemanticModel semanticModel)
-        => type.Name == TestingLibraryAssertionType && type.ContainingModule.Name == TestingLibraryModule + ".dll";
 }