go.mod: update golang.org/x dependencies

Update golang.org/x dependencies to their latest tagged versions.
Once this CL is submitted, and post-submit testing succeeds on all
first-class ports across all supported Go versions, this repository
will be tagged with its next minor version.

Change-Id: I3ff1efa287de001f5b080fc389a03231a6102ce3
Reviewed-on: https://go-review.googlesource.com/c/term/+/460496
Run-TryBot: Gopher Robot <gobot@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
diff --git a/go.mod b/go.mod
index 1174335..6801ff9 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@
 go 1.17
-require golang.org/x/sys v0.3.0
+require golang.org/x/sys v0.4.0
diff --git a/go.sum b/go.sum
index 2738fca..c2a6782 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,2 @@
-golang.org/x/sys v0.3.0 h1:w8ZOecv6NaNa/zC8944JTU3vz4u6Lagfk4RPQxv92NQ=
-golang.org/x/sys v0.3.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
+golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=