Allow paste even though unmaintained, for now

https://rustsec.org/advisories/RUSTSEC-2024-0436.html now causes
the `cargo deny advisories` check to fail (even if the separate and
more important failure from `ring` is changed by bumping the `ring`
version, as in #1878).

`paste` is mature and would be hard to remove as a transitive
dependency at this time:

    > cargo tree --invert paste --no-dedupe --depth 3
    paste v1.0.15 (proc-macro)
    └── ratatui v0.26.3
        ├── crosstermion v0.14.0
        │   ├── gitoxide v0.41.0 (C:\Users\ek\source\repos\gitoxide)
        │   └── prodash v29.0.0
        ├── prodash v29.0.0
        │   ├── gitoxide v0.41.0 (C:\Users\ek\source\repos\gitoxide)
        │   ├── gix v0.70.0 (C:\Users\ek\source\repos\gitoxide\gix)
        │   └── gix-features v0.40.0 (C:\Users\ek\source\repos\gitoxide\gix-features)
        └── tui-react v0.23.2
            ├── crosstermion v0.14.0
            └── prodash v29.0.0

As discussed in rustsec/advisory-db#2215
and leptos-rs/leptos#3685, `paste` is
widely used and there is community interest in maintaining it.

When the status changes or more information about the future of
`paste` or its alternatives is available, `deny.toml` could be
updated again (even if only with a comment).

Author: EliahKagan

deny.toml

@@ -8,7 +8,7 @@
 # More documentation for the advisories section can be found here:
 # https://embarkstudios.github.io/cargo-deny/checks/advisories/cfg.html
 [advisories]
-ignore = []
+ignore = ["RUSTSEC-2024-0436"]