ci: Re-enable the man subcommand on release builds

[langston-barrett]

Really can't figure out why it's not working, when it works just fine for the normal build.

[langston-barrett]

The issue might be that include_str! references a path in target/ rather than target/x86-unknown-linux-musl, which is used for the static/deb builds:

souffle-lint/src/man.rs

Line 6 in a61732b

const MAN: &str = include_str!("../target/assets/doc/man/souffle-lint.1");

That path might not be populated by build.rs with the musl target. Perhaps the MAN constant could have two definitions, depending on the enabled features?