Do not add readonly modifier to accessors/properties/events if TSAB.ShowModifiers is false.

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -1972,7 +1972,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 			if (this.ShowAccessibility && accessor.Accessibility != ownerAccessibility)
 				decl.Modifiers = ModifierFromAccessibility(accessor.Accessibility);
-			if (accessor.HasReadonlyModifier())
+			if (this.ShowModifiers && accessor.HasReadonlyModifier())
 				decl.Modifiers |= Modifiers.Readonly;
 			TokenRole keywordRole = kind switch {
 				MethodSemanticsAttributes.Getter => PropertyDeclaration.GetKeywordRole,
@@ -2035,7 +2035,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		static void MergeReadOnlyModifiers(EntityDeclaration decl, Accessor accessor1, Accessor accessor2)
 		{
-			if (accessor1.HasModifier(Modifiers.Readonly) && accessor1.Role == PropertyDeclaration.GetterRole && accessor2.IsNull)
+			if (accessor1.HasModifier(Modifiers.Readonly) && accessor2.IsNull)
 			{
 				accessor1.Modifiers &= ~Modifiers.Readonly;
 				decl.Modifiers |= Modifiers.Readonly;
@@ -2047,6 +2047,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				decl.Modifiers |= Modifiers.Readonly;
 			}
 		}
+
 		IndexerDeclaration ConvertIndexer(IProperty indexer)
 		{
 			IndexerDeclaration decl = new IndexerDeclaration();