fix(build): use free-text license format in Rust package metadata

The bare string `license = "Apache-2.0 WITH Commons-Clause-1.0"` is
rejected by PyPI as an invalid SPDX expression. Switch to the table
form `license = {text = "..."}` to bypass SPDX validation.

Author: polakowo

rust/pyproject.toml

@@ -6,7 +6,7 @@ build-backend = "maturin"
 name = "vectorbt-rust"
 version = "1.0.0"
 description = "Rust-accelerated kernels for vectorbt"
-license = "Apache-2.0 WITH Commons-Clause-1.0"
+license = {text = "Apache-2.0 WITH Commons-Clause-1.0"}
 authors = [
     {name = "Oleg Polakow", email = "olegpolakow@vectorbt.pro"}
 ]