Fix several typos.

pkg/analyzer/lib/src/error/codes.dart

Index: pkg/analyzer/lib/src/error/codes.dart
diff --git a/pkg/analyzer/lib/src/error/codes.dart b/pkg/analyzer/lib/src/error/codes.dart
index f86f0d9608e9bcf4afdf224d052966fd7011d173..155b8d81689ccfc8d0dfa0afc1ddfdfad57b1e35 100644
--- a/pkg/analyzer/lib/src/error/codes.dart
+++ b/pkg/analyzer/lib/src/error/codes.dart
@@ -1135,7 +1135,7 @@ class CompileTimeErrorCode extends ErrorCode {
           "This class can't implement the deferred class '{0}'.",
           "Try specifying a different interface, "
           "removing the class from the list, or "
-          "changing the import to not be deferred..");
+          "changing the import to not be deferred.");
 
   /**
    * 12.2 Null: It is a compile-time error for a class to attempt to extend or