Update package dependencies + tidy (#38)

Weekly update to the project's package dependencies initiated by an
automatic GitHub Action running on cron. Keeps upgrades less of a
monolithic task and lets security-related patches trickle in more
quickly.

Co-authored-by: Bot <bot@iandavis.com>

go.mod

@@ -2,4 +2,4 @@ module github.com/iand/microdata
 
 go 1.21.4
 
-require golang.org/x/net v0.18.0
+require golang.org/x/net v0.19.0

go.sum

@@ -1,2 +1,2 @@
-golang.org/x/net v0.18.0 h1:mIYleuAkSbHh0tCv7RvjL3F6ZVbLjq4+R7zbOn3Kokg=
-golang.org/x/net v0.18.0/go.mod h1:/czyP5RqHAH4odGYxBJ1qz0+CE5WZ+2j1YgoEo8F2jQ=
+golang.org/x/net v0.19.0 h1:zTwKpTd2XuCqf8huc7Fo2iSy+4RHPd10s4KzeTnVr1c=
+golang.org/x/net v0.19.0/go.mod h1:CfAk/cbD4CthTvqiEl8NpboMuiuOYsAr/7NOjZJtv1U=