syncthing: regenerate macr keys and update device ID

Previous secrets were encrypted with empty content, preventing
Syncthing from starting. Regenerated cert/key and re-encrypted
them with agenix.

Author: juanibiapina

nix/modules/syncthing.nix

@@ -23,7 +23,7 @@
           id = "SLTOL4R-UE3J2AS-KJEJKSN-77TVD3X-IWGYSRE-HJHQX6Z-QXEIGCJ-IZOIFQT";
         };
         macr = {
-          id = "GYFANBW-WVSVMTY-4CUDBPU-IL3CDFU-KB2OJO7-L37GTXG-7DNZOY2-PXSIBA6";
+          id = "7HLPCQJ-O67F4DE-HIL3AKA-7SJWNAA-BPL2MWY-I6GT7UQ-7ONEBDY-3EMZLQ7";
         };
       };