fix license format

Author: ClemensSchwarke

CITATION.cff

@@ -3,7 +3,7 @@ title: "RSL-RL: A Learning Library for Robotics Research"
 message: "If you use this work, please cite the following paper."
 repository-code: "https://github.com/leggedrobotics/rsl_rl"
 license: BSD-3-Clause
-version: 3.1.0
+version: 3.1.1
 type: software
 authors:
   - family-names: Schwarke

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "rsl-rl-lib"
-version = "3.1.0"
+version = "3.1.1"
 keywords = ["reinforcement-learning", "robotics"]
 maintainers = [
   { name="Clemens Schwarke", email="[email protected]" },
@@ -17,8 +17,8 @@ authors = [
   { name="David Hoeller", email="[email protected]" },
 ]
 description = "Fast and simple RL algorithms implemented in PyTorch"
-readme = { file = "README.md", content-type = "text/markdown"}
-license = { text = "BSD-3-Clause" }
+readme = { file = "README.md", content-type = "text/markdown" }
+license = "BSD-3-Clause"
 requires-python = ">=3.9"
 classifiers = [
     "Programming Language :: Python :: 3",