fix spelling in core libraries

sdk/lib/internal/symbol.dart

Index: sdk/lib/internal/symbol.dart
diff --git a/sdk/lib/internal/symbol.dart b/sdk/lib/internal/symbol.dart
index 73e702377d19b3de16de0c48da5f961a6806b9c2..85df9a71106137151900d66b82c367737e8ebd74 100644
--- a/sdk/lib/internal/symbol.dart
+++ b/sdk/lib/internal/symbol.dart
@@ -45,7 +45,7 @@ class Symbol implements core.Symbol {
    * Source of RegExp matching a declarable operator names.
    *
    * The operators that can be declared using `operator` declarations are
-   * also the only ones allowed as symbols. The name of the oeprators is
+   * also the only ones allowed as symbols. The name of the operators is
    * the same as the operator itself except for unary minus, where the name
    * is "unary-".
    */