RPM does not allow '-' in the Release field (it is the Version/Release
delimiter). The 'uos20-' prefix produced Release values like 'uos20-b1.el8'
which rpmbuild rejects with 'Illegal char '-' (0x2d)'. Switch to 'uos20.'.
PKGREL=1 + 'uos20' prefix concatenated to 'uos201', which reads as
'uos two hundred one' rather than 'uos20 version 1'. Add a hyphen
('uos20-') so the resulting release tag is 'uos20-1' / 'uos20-b12' etc.
Update compile.sh logic and the three doc references (README,
AGENTS.md, docker/README.md) to match.
The UOS 20 build was previously a near-duplicate spec (openssh.uos20.spec)
with only the kernel-panic patch as an intentional difference. The
kerberos5 and gssapi drift was unintentional and caused maintenance pain
upstream changes had to be applied in two places.
Now there is one spec. The kernel-panic patch is gated on a uos20 macro
that compile.sh sets only when UOS20=1 is in the environment, so non-UOS
builds cannot accidentally pick it up. When UOS20=1, PKGREL is prefixed
with 'uos20' so the resulting RPMs are distinguishable from the standard
build (e.g. PKGREL=1 -> uos201).
Delete openssh.uos20.spec, document UOS20=1 in AGENTS.md.
