Update pyproject.toml for 3.14t (#1417)

- Update description to include 3.14
- Add 3.14 and free-threading trove classifiers
- Update deps to switch back to pyyaml for 3.14

Author: itamaro

pyproject.toml

@@ -3,7 +3,7 @@ requires = ["setuptools", "setuptools-scm", "setuptools-rust", "wheel"]
 
 [project]
 name = "libcst"
-description = "A concrete syntax tree with AST-like properties for Python 3.0 through 3.13 programs."
+description = "A concrete syntax tree with AST-like properties for Python 3.0 through 3.14 programs."
 readme = "README.rst"
 dynamic = ["version"]
 license = { file = "LICENSE" }
@@ -15,12 +15,15 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: Free Threading",
     "Typing :: Typed",
 ]
 requires-python = ">=3.9"
 dependencies = [
     "pyyaml>=5.2; python_version < '3.13'",
-    "pyyaml-ft>=8.0.0; python_version >= '3.13'",
+    "pyyaml-ft>=8.0.0; python_version == '3.13'",
+    "pyyaml>=6.0.3; python_version >= '3.14'",
     "typing-extensions; python_version < '3.10'",
 ]