Use SPDX license expression instead of classifier

Replace deprecated license classifier with modern SPDX format:
- Remove "License :: OSI Approved :: MIT License" classifier
- Change license = {text = "MIT License"} to license = "MIT"

See: https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gijzelaerr

pyproject.toml

@@ -16,15 +16,14 @@ classifiers = [
     "Topic :: System :: Hardware",
     "Intended Audience :: Developers",
     "Intended Audience :: Manufacturing",
-    "License :: OSI Approved :: MIT License",
     "Operating System :: POSIX",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
 ]
-license = {text = "MIT License"}
+license = "MIT"
 requires-python = ">=3.10"
 keywords = ["snap7", "s7", "siemens", "plc"]