revisit the `<nonissue>` tag in OpenSSL vulnerability feed

[keshav-space]

XML response contains non issue tags, which we don't need right now.
But might want to make use of it at a later stage!

<nonissue base="0.9.8" cve="2010-0928">
</nonissue>
<nonissue base="none" cve="2002-20001" ref="https://github.com/openssl/openssl/issues/17374">
</nonissue>
<statement base="none">
</statement>
<statement base="0.9.6">
</statement>

[keshav-space]

No longer applicable, OpenSSL has removed XML feed: https://www.openssl.org/news/vulnerabilities.xml

Instead, we now have a fresh v2 importer for OpenSSL to import secjson advisories from https://github.com/openssl/release-metadata/tree/main/secjson. See #2119