Revert "fix: improve datetime detection in pandas dataframes"

This reverts commit 602d2c1.

src/pyobsplot/data.py

@@ -60,7 +60,7 @@ def pd_to_arrow(df: pd.DataFrame) -> bytes:
     """
     # Convert dates to timestamps
     for col in df.columns:
-        if pd.api.types.is_datetime64_any_dtype(df[col]):
+        if df[col].dtype == "object":
             try:
                 df[col] = pd.to_datetime(df[col])
             except ValueError: