nixos/tsm-{client,backup}: update links in module comments

IBM has changed the URL structures of their support web pages.
The commit at hand updates URLs in two comments
so they follow the new structure.

nixos/modules/programs/tsm-client.nix

@@ -144,7 +144,7 @@ let
     };
     config.name = mkDefault name;
     # Client system-options file directives are explained here:
-    # https://www.ibm.com/support/knowledgecenter/SSEQVQ_8.1.8/client/c_opt_usingopts.html
+    # https://www.ibm.com/docs/en/spectrum-protect/8.1.13?topic=commands-processing-options
     config.extraConfig =
       mapAttrs (lib.trivial.const mkDefault) (
         {

nixos/modules/services/backup/tsm.nix

@@ -88,7 +88,7 @@ in
       # TSM needs a HOME dir to store certificates.
       environment.HOME = "/var/lib/tsm-backup";
       # for exit status description see
-      # https://www.ibm.com/support/knowledgecenter/en/SSEQVQ_8.1.8/client/c_sched_rtncode.html
+      # https://www.ibm.com/docs/en/spectrum-protect/8.1.13?topic=clients-client-return-codes
       serviceConfig.SuccessExitStatus = "4 8";
       # The `-se` option must come after the command.
       # The `-optfile` option suppresses a `dsm.opt`-not-found warning.