Fix test failure, address feedback

Author: calda

Sources/SwiftSyntaxMacroExpansion/MacroExpansion.swift

@@ -407,7 +407,7 @@ public func expandAttachedMacroWithoutCollapsing<Context: MacroExpansionContext>
         // Create an implicit `AccessorDeclSyntax` to use for the macro expansion
         // of this computed var decl
         let getterDecl = AccessorDeclSyntax(
-          accessorSpecifier: .keyword(.get),
+          accessorSpecifier: .keyword(.get, presence: .missing),
           body: CodeBlockSyntax(
             leftBrace: accessorBlock.leftBrace,
             statements: stmts,

Sources/SwiftSyntaxMacros/Syntax+LexicalContext.swift

@@ -67,7 +67,7 @@ extension SyntaxProtocol {
       varDecl = varDecl.detached
       varDecl.bindings = PatternBindingListSyntax(
         varDecl.bindings.map {
-          var binding = $0
+          var binding = $0.detached
           binding.accessorBlock = nil
           binding.initializer = nil
           return binding

Tests/SwiftSyntaxMacroExpansionTest/LexicalContextTests.swift

@@ -547,6 +547,7 @@ final class LexicalContextTests: XCTestCase {
               try _
               unsafe _
               contextDescription: String
+              var contextDescription: String
               struct S {}
               { c in
               }