Make hocr API experimental for now

This commit can be reverted when we are ready to release a new version.

src/ocrmypdf/api.py

@@ -375,7 +375,7 @@ def ocr(  # noqa: D417
         return run_pipeline(options=options, plugin_manager=plugin_manager)
 
 
-def pdf_to_hocr(  # noqa: D417
+def _pdf_to_hocr(  # noqa: D417
     input_pdf: Path,
     output_folder: Path,
     *,
@@ -432,6 +432,8 @@ def pdf_to_hocr(  # noqa: D417
     For arguments not explicitly documented here, see documentation for the
     equivalent command line parameter.
 
+    This API is **experimental** and subject to change.
+
     Args:
         input_pdf: Input PDF file path.
         output_folder: Output folder path.
@@ -468,7 +470,7 @@ def pdf_to_hocr(  # noqa: D417
         return run_hocr_pipeline(options=options, plugin_manager=plugin_manager)
 
 
-def hocr_to_ocr_pdf(  # noqa: D417
+def _hocr_to_ocr_pdf(  # noqa: D417
     work_folder: Path,
     output_file: Path,
     *,
@@ -496,6 +498,8 @@ def hocr_to_ocr_pdf(  # noqa: D417
     For arguments not explicitly documented here, see documentation for the
     equivalent command line parameter.
 
+    This API is **experimental** and subject to change.
+
     Args:
         work_folder: Work folder path, as generated by :func:`pdf_to_hocr`.
         output_file: Output PDF file path.
@@ -543,8 +547,6 @@ __all__ = [
     'get_parser',
     'get_plugin_manager',
     'ocr',
-    'pdf_to_hocr',
     'run_pipeline',
     'run_pipeline_cli',
-    'hocr_to_ocr_pdf',
 ]