Migrate to SPDX license specifier in pyproject.toml (#10768)

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name        = "esphome"
-license     = {text = "MIT"}
+license     = "MIT"
 description = "ESPHome is a system to configure your microcontrollers by simple yet powerful configuration files and control them remotely through Home Automation systems."
 readme      = "README.md"
 authors     = [
@@ -15,7 +15,6 @@ classifiers = [
     "Environment :: Console",
     "Intended Audience :: Developers",
     "Intended Audience :: End Users/Desktop",
-    "License :: OSI Approved :: MIT License",
     "Programming Language :: C++",
     "Programming Language :: Python :: 3",
     "Topic :: Home Automation",