_content/doc/modules: add missing @ in replace command

Change-Id: I96f1559e42a46eba327795d953b45eebd034af0e
Reviewed-on: https://go-review.googlesource.com/c/website/+/330049
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
diff --git a/_content/doc/modules/managing-dependencies.md b/_content/doc/modules/managing-dependencies.md
index 5f848a6..6955dd5 100644
--- a/_content/doc/modules/managing-dependencies.md
+++ b/_content/doc/modules/managing-dependencies.md
@@ -360,7 +360,7 @@
 ```
 $ go list -m example.com/theirmodule
 example.com/theirmodule v1.2.3
-$ go mod edit -replace=example.com/theirmodule@v1.2.3=example.com/myfork/theirmodule v1.2.3-fixed
+$ go mod edit -replace=example.com/theirmodule@v1.2.3=example.com/myfork/theirmodule@v1.2.3-fixed
 ```
 
 **Note:** When you use the `replace` directive, Go tools don't authenticate