Moves EmptyNostrClient to a class to avoid auto-import issues

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip46RemoteSigner/signer/ConvertExceptionsTest.kt

@@ -34,7 +34,7 @@ class ConvertExceptionsTest {
         NostrSignerRemote.fromBunkerUri(
             "bunker://${"a".repeat(64)}?relay=wss://r.com",
             NostrSignerInternal(KeyPair()),
-            EmptyNostrClient,
+            EmptyNostrClient(),
         )
 
     @Test

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip46RemoteSigner/signer/FromBunkerUriTest.kt

@@ -30,7 +30,7 @@ import kotlin.test.assertNull
 
 class FromBunkerUriTest {
     private val signer = NostrSignerInternal(KeyPair())
-    private val client = EmptyNostrClient
+    private val client = EmptyNostrClient()
     private val validHex = "a".repeat(64)
 
     @Test