note supported grype versions (#2287)

Signed-off-by: Alex Goodman <[email protected]>

README.md

@@ -212,7 +212,7 @@ grype --add-cpes-if-none --distro alpine:3.10 sbom:some-alpine-3.10.spdx.json
 
 ### Supported versions
 
-Any version of Grype before v0.40.1 is not supported. Unsupported releases will not receive any software updates or
+Any version of Grype before v0.51.0 (Oct 2022) is not supported. Unsupported releases will not receive any software updates or
 vulnerability database updates. You can still build vulnerability databases for unsupported Grype releases by using previous
 releases of [vunnel](https://github.com/anchore/vunnel) to gather the upstream data and [grype-db](https://github.com/anchore/grype-db)
 to build databases for unsupported schemas.