packaging: use an SPDX license expression instead of classifiers

Replace the "License :: OSI Approved" classifiers with a PEP 639
SPDX license expression. The project is Apache-2.0 overall, but two
files (nix_expression.py, yocto_recipe.py) carry their own standalone
MIT headers, so the correct expression is "Apache-2.0 AND MIT" (not
"OR" -- it's not a licensee's choice, different files are under
different licenses). Bumps the setuptools build requirement to >=77,
which is what added SPDX license-expression support.

Assisted-by: Claude:claude-opus-5
AI-Generated: Uses Claude (claude-opus-5)
Signed-off-by: Rob Woolley <rob.woolley@windriver.com>

Author: robwoolley

pyproject.toml

@@ -1,20 +1,18 @@
 [build-system]
-requires = ["setuptools>=64", "setuptools-scm>=8"]
+requires = ["setuptools>=77", "setuptools-scm>=8"]
 build-backend = "setuptools.build_meta"
 
 [project]
 name = "superflore"
 description = "Super Bloom"
 readme = "README.md"
-license = { text = "Apache 2.0" }
+license = "Apache-2.0 AND MIT"
 authors = [
     { name = "Hunter L. Allen", email = "hunterlallen@protonmail.com" },
 ]
 keywords = ["ROS"]
 classifiers = [
     "Programming Language :: Python",
-    "License :: OSI Approved :: Apache Software License",
-    "License :: OSI Approved :: MIT License",
 ]
 requires-python = ">=3"
 dynamic = ["version"]