content: fix code block in Publishing Go Modules article

When indentation is used to create a code block immediately following
a list, Markdown syntax is ambiguous: it can be interpreted as another
text paragraph belonging to the last list entry, or as a standalone
code block.

The original behavior in CL 197637 made this unambiguously a code block
because the present format did not support lists. This changed when the
article was converted to use Markdown syntax in CL 222848.

Start using a fenced code block instead of indentation to resolve the
Markdown ambiguity and restore original behavior.

For golang/go#33955.

Change-Id: I9537bc72d7a32f90592942591b2688fb2f26c452
Reviewed-on: https://go-review.googlesource.com/c/blog/+/245017
Reviewed-by: Jean de Klerk <deklerk@google.com>
diff --git a/content/publishing-go-modules.article b/content/publishing-go-modules.article
index 951a085..a215072 100644
--- a/content/publishing-go-modules.article
+++ b/content/publishing-go-modules.article
@@ -162,14 +162,16 @@
 
 4. Push the new tag to the origin repository.
 
-	$ go mod tidy
-	$ go test ./...
-	ok      example.com/hello       0.015s
-	$ git add go.mod go.sum hello.go hello_test.go
-	$ git commit -m "hello: changes for v0.1.0"
-	$ git tag v0.1.0
-	$ git push origin v0.1.0
-	$
+```
+$ go mod tidy
+$ go test ./...
+ok      example.com/hello       0.015s
+$ git add go.mod go.sum hello.go hello_test.go
+$ git commit -m "hello: changes for v0.1.0"
+$ git tag v0.1.0
+$ git push origin v0.1.0
+$
+```
 
 Now other projects can depend on `v0.1.0` of `example.com/hello`. For your own
 module, you can run `go list -m example.com/hello@v0.1.0` to confirm the latest