Revert "SwiftSyntax: Fix resilient build"

This reverts commit bbb21c8.

Author: slavapestov

tools/SwiftSyntax/Diagnostic.swift

@@ -109,8 +109,7 @@ public enum FixIt: Codable {
   /// it is a range with the same start and end location.
   public var range: SourceRange {
     switch self {
-    case .remove(let range): return range
-    case .replace(let range, _): return range
+    case .remove(let range), .replace(let range, _): return range
     case .insert(let loc, _): return SourceRange(start: loc, end: loc)
     }
   }