go.mod: update golang.org/x dependencies

Update golang.org/x dependencies to their latest tagged versions.

Change-Id: I14df917f913018c164a9bb9bf040de780ee54b9c
Reviewed-on: https://go-review.googlesource.com/c/image/+/633479
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
diff --git a/go.mod b/go.mod
index b1dc92e..06b19cd 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@
 
 go 1.18
 
-require golang.org/x/text v0.20.0
+require golang.org/x/text v0.21.0
diff --git a/go.sum b/go.sum
index 63d9de6..0d8f5b2 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,2 @@
-golang.org/x/text v0.20.0 h1:gK/Kv2otX8gz+wn7Rmb3vT96ZwuoxnQlY+HlJVj7Qug=
-golang.org/x/text v0.20.0/go.mod h1:D4IsuqiFMhST5bX19pQ9ikHC2GsaKyk/oF+pn3ducp4=
+golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
+golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=