_content/doc/modules: fix typo in gomod-ref.md

Fix typo in the description of the sample replace directive.

Change-Id: Ifce15609e096253c07137bf6727568bde58982c3
GitHub-Last-Rev: 54973c41cf
GitHub-Pull-Request: golang/website#38
Reviewed-on: https://go-review.googlesource.com/c/website/+/292991
Reviewed-by: Steve Traut <straut@google.com>
Trust: Dmitri Shuralyov <dmitshur@golang.org>

_content/doc/modules/gomod-ref.md

@@ -242,7 +242,7 @@ replacement path when resolving the dependency.
   replace example.com/othermodule => example.com/othermodule v1.2.3
   ```
 
-  The following example replaces module version v1.2.5 with version v1.2.5 of
+  The following example replaces module version v1.2.5 with version v1.2.3 of
   the same module.
 
   ```