Fix typo in documentation.

sdk/lib/core/errors.dart

Index: sdk/lib/core/errors.dart
diff --git a/sdk/lib/core/errors.dart b/sdk/lib/core/errors.dart
index c1dff429de345ceef660bb44fb5c3bb638312b69..16f2ffb09934139627dd4ec0a84e388cd622b8ea 100644
--- a/sdk/lib/core/errors.dart
+++ b/sdk/lib/core/errors.dart
@@ -222,7 +222,7 @@ class RangeError extends ArgumentError {
                     (message != null) ? message : "Value not in range");
 
   /**
-   * Create a new [RangeError] with for an invalid value being outside a range.
+   * Create a new [RangeError] for a value being outside the valid range.
    *
    * The allowed range is from [minValue] to [maxValue], inclusive.
    * If `minValue` or `maxValue` are `null`, the range is infinite in