vim-patch:9.1.1544: :retab cannot be limited to indentation only (#34939)

Problem:  :retab cannot be limited to indentation only
Solution: add the optional -indentonly parameter
          (Hirohito Higashi)

closes: vim/vim#17730

836e54f5de

Co-authored-by: Hirohito Higashi <h.east.727@gmail.com>

src/nvim/cmdexpand_defs.h

@@ -114,6 +114,7 @@ enum {
   EXPAND_FINDFUNC,
   EXPAND_FILETYPECMD,
   EXPAND_PATTERN_IN_BUF,
+  EXPAND_RETAB,
   EXPAND_CHECKHEALTH,
   EXPAND_LUA,
 };