Remove a work-around for a long-ago fixed issue (dart-lang/pubspec_parse#42)

pkgs/pubspec_parse/lib/src/dependency.dart

diff --git a/pkgs/pubspec_parse/lib/src/dependency.dart b/pkgs/pubspec_parse/lib/src/dependency.dart
index d9b3db2..52057eb 100644
--- a/pkgs/pubspec_parse/lib/src/dependency.dart
+++ b/pkgs/pubspec_parse/lib/src/dependency.dart
@@ -21,15 +21,7 @@
           // This is likely a "synthetic" map created from a String value
           // Use `source` to throw this exception with an actual YamlMap and
           // extract the associated error information.
-
-          var message = e.message;
-          final innerError = e.innerError;
-          // json_annotation should handle FormatException...
-          // https://github.com/dart-lang/json_serializable/issues/233
-          if (innerError is FormatException) {
-            message = innerError.message;
-          }
-          throw CheckedFromJsonException(source, key, e.className, message);
+          throw CheckedFromJsonException(source, key, e.className, e.message);
         }
         rethrow;
       }