Refactor error messages and function signatures across multiple notebooks for clarity and consistency

- Updated error messages in Gauss method and numerical methods to use variables for better readability.
- Added return type hints to function signatures in various notebooks to improve code documentation.
- Corrected minor grammatical issues in docstrings for better clarity.
- Adjusted print statements and list concatenations for improved output formatting.
- Enhanced plotting functions to ensure consistent figure handling.

L3/Statistiques/TP2.ipynb

@@ -220,7 +220,7 @@
    },
    "outputs": [],
    "source": [
-    "def simule(a, b, n):\n",
+    "def simule(a, b, n) -> None:\n",
     "    X = np.random.gamma(a, 1 / b, n)\n",
     "    intervalle = np.linspace(0, np.max(X), 100)\n",
     "    plt.hist(X, bins=intervalle, density=True, label=\"Echantillon de X\")\n",