jose: disable man page generation via asciidoc
The asciidoc/a2x toolchain bundled with newer Python (3.14) is
incompatible with jose's docbook XSL configuration, causing the
build to fail with xsltproc returning non-zero status while
processing 'jose.1.xml'.
Since the man pages are not strictly required for OpenWrt (and
typically stripped from the final image anyway), unconditionally
disable a2x detection in meson.build via a disabler() so that the
'mans' list stays empty regardless of host tooling.
Link: https://github.com/latchset/jose
Signed-off-by: Daniel Golle <redacted>