fix(py): mark sqlshield-py as publish = false (PyPI-only crate)

`sqlshield-py` is a PyO3 cdylib distributed as a Python wheel via
maturin / PyPI. The crate-type is `cdylib`, so no Rust crate can
depend on it — publishing it to crates.io adds nothing and just
made the release-plz workflow attempt a redundant publish. Setting
`publish = false` tells cargo (and release-plz) to skip it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: davidsmfreire

sqlshield-py/Cargo.toml

@@ -7,6 +7,7 @@ rust-version.workspace = true
 license.workspace = true
 repository.workspace = true
 description = "Python bindings for sqlshield with cli included"
+publish = false
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 [lib]