content: replace curly with straight double quote

Change-Id: I570bc25034c663d2fe184f340ebf64b2f5a630f3
GitHub-Last-Rev: ae83fcccadba5e4acbe959268ba6ceb41ef70e07
GitHub-Pull-Request: golang/blog#26
Reviewed-on: https://go-review.googlesource.com/c/blog/+/201897
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/content/go1.13-errors.article b/content/go1.13-errors.article
index 32e18eb..fd3fc4c 100644
--- a/content/go1.13-errors.article
+++ b/content/go1.13-errors.article
@@ -184,7 +184,7 @@
 
 Wrapping an error with `%w` makes it available to `errors.Is` and `errors.As`:
 
-    err := fmt.Errorf("access denied: %w”, ErrPermission)
+    err := fmt.Errorf("access denied: %w", ErrPermission)
     ...
     if errors.Is(err, ErrPermission) ...