fix help hint showing shadowed option name

when a subcommand option shadows a help option name (e.g. -h),
the error hint was still suggesting the shadowed name. now it
uses get_help_option_names() which filters out names claimed
by other options, so it picks a working alternative like --help.

Author: Mr-Neutr0n

src/click/exceptions.py

@@ -78,8 +78,9 @@ def show(self, file: t.IO[t.Any] | None = None) -> None:
             self.ctx is not None
             and self.ctx.command.get_help_option(self.ctx) is not None
         ):
+            help_names = self.ctx.command.get_help_option_names(self.ctx)
             hint = _("Try '{command} {option}' for help.").format(
-                command=self.ctx.command_path, option=self.ctx.help_option_names[0]
+                command=self.ctx.command_path, option=help_names[0]
             )
             hint = f"{hint}\n"
         if self.ctx is not None: