Replace leptonica deskew with tesseract find skew and pillow rotate

Also rebuild the cache.

src/ocrmypdf/pluginspec.py

@@ -366,6 +366,11 @@ class OcrEngine(ABC):
     def get_orientation(input_file: Path, options: Namespace) -> OrientationConfidence:
         """Returns the orientation of the image."""
 
+    @staticmethod
+    def get_deskew(input_file: Path, options: Namespace) -> float:
+        """Returns the deskew angle of the image, in radians."""
+        return 0.0
+
     @staticmethod
     @abstractmethod
     def generate_hocr(