Swift: skip MacroExpansionExpr/MacroExpansionDecl

They only appear in an intermediate AST and disappear as soon as the
macro is expanded.
The only way to get these in is to construct an "incorrect" AST, e.g.:

```
let x = #does_not_exist() // MacroExpansionExpr
struct S {
  #does_not_exist() // MacroExpansionDecl
}
```

Author: AlexDenisov

swift/extractor/infra/SwiftTagTraits.h

@@ -196,7 +196,7 @@ MAP(swift::Expr, ExprTag)
   MAP(swift::OneWayExpr, OneWayExprTag)
   MAP(swift::TapExpr, TapExprTag)
   MAP(swift::TypeJoinExpr, void)  // TODO (introduced in 5.8)
-  MAP(swift::MacroExpansionExpr, void)  // TODO (introduced in 5.8)
+  MAP(swift::MacroExpansionExpr, void) // unexpanded macro in an expr context, skipping
   MAP(swift::CopyExpr, CopyExprTag)
   MAP(swift::ConsumeExpr, ConsumeExprTag)
   MAP(swift::MaterializePackExpr, void)  // TODO (introduced in 5.9)
@@ -243,10 +243,8 @@ MAP(swift::Decl, DeclTag)
     MAP(swift::InfixOperatorDecl, InfixOperatorDeclTag)
     MAP(swift::PrefixOperatorDecl, PrefixOperatorDeclTag)
     MAP(swift::PostfixOperatorDecl, PostfixOperatorDeclTag)
-  MAP(swift::MacroExpansionDecl, void)  // TODO (introduced in 5.8)
-#if CODEQL_SWIFT_VERSION_GE(5, 9)
-  MAP(swift::MissingDecl, void)  // TODO (introduced in 5.9)
-#endif
+  MAP(swift::MacroExpansionDecl, void) // unexpanded macro in a decl context, skipping
+  MAP(swift::MissingDecl, void) // appears around an unexpanded macro, skipping
 
 MAP(swift::Pattern, PatternTag)
   MAP(swift::ParenPattern, ParenPatternTag)