doc: Fix missing comma in JSON example in REST-interface.md

This pull request addresses a minor issues in the REST-interface.md documentation:

Missing Comma in JSON Example: In the "Query UTXO set" section, a missing comma after the "desc" field in the JSON example has been added to ensure valid JSON syntax.

doc/REST-interface.md

@@ -117,7 +117,7 @@ $ curl localhost:18332/rest/getutxos/checkmempool/b2cdfd7b89def827ff8af7cd9bff76
          "value" : 8.8687,
          "scriptPubKey" : {
             "asm" : "OP_DUP OP_HASH160 1c7cebb529b86a04c683dfa87be49de35bcf589e OP_EQUALVERIFY OP_CHECKSIG",
-            "desc" : "addr(mi7as51dvLJsizWnTMurtRmrP8hG2m1XvD)#gj9tznmy"
+            "desc" : "addr(mi7as51dvLJsizWnTMurtRmrP8hG2m1XvD)#gj9tznmy",
             "hex" : "76a9141c7cebb529b86a04c683dfa87be49de35bcf589e88ac",
             "type" : "pubkeyhash",
             "address" : "mi7as51dvLJsizWnTMurtRmrP8hG2m1XvD"