chore(deps): Update stable-baselines3 requirement

Updates the requirements on [stable-baselines3](https://github.com/DLR-RM/stable-baselines3) to permit the latest version.
- [Release notes](https://github.com/DLR-RM/stable-baselines3/releases)
- [Commits](https://github.com/DLR-RM/stable-baselines3/compare/v2.8.0...v2.9.0)

---
updated-dependencies:
- dependency-name: stable-baselines3
  dependency-version: 2.9.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/docs.yml

@@ -33,7 +33,7 @@ jobs:
         python-version: "3.10"
 
     - name: Cache pip dependencies
-      uses: actions/cache@v6
+      uses: actions/cache@v5
       with:
         path: ~/.cache/pip
         key: ${{ runner.os }}-pip-docs-${{ hashFiles('**/pyproject.toml') }}

.github/workflows/lint.yml

@@ -24,7 +24,7 @@ jobs:
         python-version: "3.10"
 
     - name: Cache pip dependencies
-      uses: actions/cache@v6
+      uses: actions/cache@v5
       with:
         path: ~/.cache/pip
         key: ${{ runner.os }}-pip-lint-${{ hashFiles('**/pyproject.toml') }}

.github/workflows/security.yml

@@ -27,7 +27,7 @@ jobs:
         python-version: "3.10"
 
     - name: Cache pip dependencies
-      uses: actions/cache@v6
+      uses: actions/cache@v5
       with:
         path: ~/.cache/pip
         key: ${{ runner.os }}-pip-security-${{ hashFiles('**/requirements.txt') }}

requirements/rl.txt

@@ -8,7 +8,7 @@
 # Only install if you want to use full PPO/A2C/SAC training.
 
 # Core RL library
-stable-baselines3[extra]>=2.8.0
+stable-baselines3[extra]>=2.9.0
 
 # Gymnasium environment (OpenAI Gym successor)
 gymnasium>=0.29.1