content: fix numbering on v2 post

Change-Id: Ic338e840a45ddf4f7da2de18941c352fab882bfb
Reviewed-on: https://go-review.googlesource.com/c/blog/+/205919
Reviewed-by: Andrew Bonventre <andybons@golang.org>
diff --git a/content/v2-go-modules.article b/content/v2-go-modules.article
index f66f134..634c3dc 100644
--- a/content/v2-go-modules.article
+++ b/content/v2-go-modules.article
@@ -13,7 +13,7 @@
 - Part 1 — [[/using-go-modules][Using Go Modules]]
 - Part 2 — [[/migrating-to-go-modules][Migrating To Go Modules]]
 - Part 3 — [[/publishing-go-modules][Publishing Go Modules]]
-- *Part*3*—*Go*Modules:*v2*and*Beyond* (this post)
+- *Part*4*—*Go*Modules:*v2*and*Beyond* (this post)
 
 As a successful project matures and new requirements are added, past features
 and design decisions might stop making sense. Developers may want to integrate