Remove usages of spans.

Author: JohanLarsson

AspNetCoreAnalyzers/Helpers/StringLiteral.cs

@@ -1,6 +1,5 @@
 namespace AspNetCoreAnalyzers
 {
-    using System;
     using Microsoft.CodeAnalysis;
     using Microsoft.CodeAnalysis.CSharp.Syntax;
     using Microsoft.CodeAnalysis.Text;
@@ -14,10 +13,6 @@ public StringLiteral(LiteralExpressionSyntax literalExpression)
 
         public LiteralExpressionSyntax LiteralExpression { get; }
 
-        public ReadOnlySpan<char> Text => this.LiteralExpression.Token.Text.AsSpan();
-
-        public ReadOnlySpan<char> ValueText => this.LiteralExpression.Token.ValueText.AsSpan();
-
         public bool IsVerbatim
         {
             get
@@ -85,4 +80,4 @@ int GetIndex(int pos)
             }
         }
     }
-}
+}

AspNetCoreAnalyzers/Helpers/StringLiteralSpan.cs

@@ -2,7 +2,6 @@ namespace AspNetCoreAnalyzers
 {
     using System;
     using Microsoft.CodeAnalysis;
-    using Microsoft.CodeAnalysis.CSharp.Syntax;
     using Microsoft.CodeAnalysis.Text;
 
     public struct StringLiteralSpan : IEquatable<StringLiteralSpan>