build: Update all dependencies (#7968)

Also add a script step for how to do this, as frankly I forget each time
what the canonical way is.

`go run build.go update-deps`

lib/db/structs.pb.go

@@ -8,10 +8,10 @@ import (
 	_ "github.com/gogo/protobuf/gogoproto"
 	proto "github.com/gogo/protobuf/proto"
 	github_com_gogo_protobuf_types "github.com/gogo/protobuf/types"
-	_ "github.com/golang/protobuf/ptypes/timestamp"
 	github_com_syncthing_syncthing_lib_protocol "github.com/syncthing/syncthing/lib/protocol"
 	protocol "github.com/syncthing/syncthing/lib/protocol"
 	_ "github.com/syncthing/syncthing/proto/ext"
+	_ "google.golang.org/protobuf/types/known/timestamppb"
 	io "io"
 	math "math"
 	math_bits "math/bits"