pycriu: add missing protobuf dependency.

pycriu requires protobuf to function. Currently, it throws an
error because protobuf is not installed by default. Adding it
to dependencies ensures it will be installed automatically.

Signed-off-by: Andrii Herheliuk <andrii@herheliuk.com>

Author: Your Name

lib/pyproject.toml

@@ -11,6 +11,7 @@ authors = [
 license = {text = "GPLv2"}
 dynamic = ["version"]
 requires-python = ">=3.6"
+dependencies = ["protobuf"]
 
 [tool.setuptools]
 packages = ["pycriu", "pycriu.images"]