Remove documentation for non-existing socket class attributes (GH-28029)

The functions in question are available on the module-level only.
(cherry picked from commit 34d82ce)

Co-authored-by: Matti Picus <[email protected]>

Author: miss-islington

Modules/socketmodule.c

@@ -151,9 +151,6 @@ getblocking() -- return True if socket is blocking, False if non-blocking\n\
 setsockopt(level, optname, value[, optlen]) -- set socket options\n\
 settimeout(None | float) -- set or clear the timeout\n\
 shutdown(how) -- shut down traffic in one or both directions\n\
-if_nameindex() -- return all network interface indices and names\n\
-if_nametoindex(name) -- return the corresponding interface index\n\
-if_indextoname(index) -- return the corresponding interface name\n\
 \n\
  [*] not available on all platforms!");