add valkey classifier

[witchcraze]

Description

add valkey classifier

$ go run cmd/syft/main.go -q valkey/valkey:9.0.0 | grep 'valkey'
valkey                   9.0.0                        binary
$ go run cmd/syft/main.go -q valkey/valkey:8.0.0 | grep 'valkey'
valkey                  8.0.0                  binary
$ go run cmd/syft/main.go -q valkey/valkey:7.2.9 | grep 'valkey'
valkey                  7.2.9                   binary

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (please discuss with the team first; Syft is 1.0 software and we won't accept breaking changes without going to 2.0)
• Documentation (updates the documentation)
• Chore (improve the developer experience, fix a test flake, etc, without changing the visible behavior of Syft)
• Performance (make Syft run faster or use less memory, without changing visible behavior much)

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

Issue references

This will fix #3400

[wasup-yash]

LGTM(not official reviewer, skimmed through the code,not tested on the sys.)