update node classifier to support 6.x

[witchcraze]

Signed-off-by: witchcraze witchcraze@gmail.com

Description

This PR is update of #3284.
Sorry, I missed 6.x series.

• Fixes Support node 6.x versions #3404

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have added unit tests that cover changed behavior
• I have tested my code in common scenarios and confirmed there are no regressions
• I have added comments to my code, particularly in hard-to-understand sections

---

$ go run cmd/syft/main.go -q node:6.2.2 | grep 'node '
node                          6.2.2                       binary
$ go run cmd/syft/main.go -q node:6.3.0 | grep 'node '
node                          6.3.0                       binary
$ go run cmd/syft/main.go -q node:6.4.0 | grep 'node '
node                          6.4.0                       binary
$ go run cmd/syft/main.go -q node:6.5.0 | grep 'node '
node                          6.5.0                       binary
$ go run cmd/syft/main.go -q node:6.6.0 | grep 'node '
node                          6.6.0                       binary
$ go run cmd/syft/main.go -q node:6.7.0 | grep 'node '
node                          6.7.0                       binary
$ go run cmd/syft/main.go -q node:6.8.0 | grep 'node '
node                          6.8.0                       binary
$ go run cmd/syft/main.go -q node:6.9.1 | grep 'node '
node                          6.9.1                       binary
$ go run cmd/syft/main.go -q node:6.9.2 | grep 'node '
node                          6.9.2                       binary
$ go run cmd/syft/main.go -q node:6.17 | grep 'node '
node                          6.17.1                          binary