go.mod: format require section

Change-Id: Ia54ecb1cd5f05c2502acd13f1cf3db5f66070d15
Reviewed-on: https://go-review.googlesource.com/c/arch/+/668335
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Sean Liao <sean@liao.dev>

go.mod

diff --git a/go.mod b/go.mod
index 72642f7..bcca36b 100644
--- a/go.mod
+++ b/go.mod
@@ -2,6 +2,7 @@
 
 go 1.23.0
 
-require rsc.io/pdf v0.1.1
-
-require gopkg.in/yaml.v3 v3.0.1
+require (
+	gopkg.in/yaml.v3 v3.0.1
+	rsc.io/pdf v0.1.1
+)