DOC: added comment to LongTableBuilder.middle_separator() (pandas-dev#34360)

Author: jeschwar

pandas/io/formats/latex.py

@@ -476,6 +476,10 @@ def _caption_and_label(self) -> str:
     @property
     def middle_separator(self) -> str:
         iterator = self._create_row_iterator(over="header")
+
+        # the content between \endfirsthead and \endhead commands
+        # mitigates repeated List of Tables entries in the final LaTeX
+        # document when dealing with longtable environments; GH #34360
         elements = [
             "\\midrule",
             "\\endfirsthead",