plugins: rename plugin nostr cosigner, minor tweaks

electrum/plugins/audio_modem/manifest.json

@@ -3,6 +3,7 @@
   "fullname": "Audio MODEM",
   "description": "Provides support for air-gapped transaction signing.",
   "requires": [["amodem", "http://github.com/romanz/amodem/"]],
+  "author":"Roman Zeyde",
   "icon":"speaker.png",
   "available_for": ["qt"]
 }

electrum/plugins/psbt_nostr/manifest.json

@@ -1,6 +1,6 @@
 {
-  "name": "nostr_multisig",
-  "fullname": "Nostr Multisig",
+  "name": "psbt_nostr",
+  "fullname": "Nostr Cosigner",
   "description": "This plugin facilitates the use of multi-signatures wallets. It sends and receives partially signed transactions from/to your cosigner wallet. PSBTs are sent and retrieved from Nostr relays.",
   "author": "The Electrum Developers",
   "icon":"nostr_multisig.png",