Rename csv to txt (not csv)

Author: Sparks29032

src/diffpy/pdfmorph/pdfmorph_io.py

@@ -249,7 +249,7 @@ def multiple_morph_output(
         header = "# Data generated by pdfmorph\n"
         header += f"# from morphing {morph_path_name}\n"
         header += f"# with target directory {target_path_name}"
-        reference_table = Path(save_directory).joinpath("Morph_Reference_Table.csv")
+        reference_table = Path(save_directory).joinpath("Morph_Reference_Table.txt")
         with open(reference_table, "w") as reference:
             print(f"{header}\n{inputs}\n{verbose_outputs}{table}", file=reference)