Add an explanatory comment about CVSS metric precedence

Co-authored-by: Nicholas McDonnell <50747025+mcdonnnj@users.noreply.github.com>

Author: dav3r

src/cyhy_cvesync/cve_sync.py

@@ -20,6 +20,7 @@
 ALLOWED_URL_SCHEMES = ["http", "https"]
 CVE_URL_RETRY_WAIT_SEC = 5
 MAX_CVE_URL_RETRIES = 10
+# Preferred CVSS metrics listed in order of preference
 PREFERRED_CVSS_METRICS = ["cvssMetricV31", "cvssMetricV30", "cvssMetricV2"]
 
 # Map to track existing CVE documents that were not updated