chore: mark property as deprecated

URL stored in the native OS secrets store is now superseded by
the URL stored in the JSON backed settings store.

Author: fioan89

src/main/kotlin/com/coder/toolbox/store/CoderSecretsStore.kt

@@ -8,6 +8,10 @@ import java.net.URL
  * Provides Coder secrets backed by the secrets store service.
  */
 class CoderSecretsStore(private val store: PluginSecretStore) {
+    @Deprecated(
+        message = "The URL is now stored the JSON backed settings store. Use CoderSettingsStore#lastDeploymentURL",
+        replaceWith = ReplaceWith("context.settingsStore.lastDeploymentURL")
+    )
     val lastDeploymentURL: String = store["last-deployment-url"] ?: ""
 
     fun tokenFor(url: URL): String? = store[url.host]