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: I693f904964c4c6d4920034a424a9f3e95825a268
Reviewed-on: https://go-review.googlesource.com/c/term/+/473435
Auto-Submit: Gopher Robot <gobot@golang.org>
Run-TryBot: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

go.mod

@@ -2,4 +2,4 @@ module golang.org/x/term
 
 go 1.17
 
-require golang.org/x/sys v0.4.0
+require golang.org/x/sys v0.6.0

go.sum

@@ -1,2 +1,2 @@
-golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
-golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0 h1:MVltZSvRTcU2ljQOhs94SXPftV6DCNnZViHeQps87pQ=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=