nginx: update CPE ID

nginx: update CPE ID

Looking at the official CPE dictionary [1], `cpe:/a:nginx:nginx` was
only used until 1.21.4 inclusively. Later it was renamed to
`cpe:/a:f5:nginx`, and it showed up in a few more non-contiguous
versions numbers after 1.21.4.

In all nginx security advisories [2] starting from year 2024, the CPE
ID used is `cpe:/a:f5:nginx_open_source`. This includes versions 1.25.0
and newer.

Update the CPE ID to the newest known value of `cpe:/a:f5:nginx_open_source`
used in nginx's own security advirosies/CVEs.

[1]: https://nvd.nist.gov/products/cpe
[2]: https://nginx.org/en/security_advisories.html

Signed-off-by: Roman Azarenko <[email protected]>