refactor(Print): Read provider values from provider

lib/plugins/print/print.js

@@ -50,11 +50,12 @@ class Print {
     if (typeof this.cache.serviceProvider === 'string') {
       service.provider = { name: this.cache.serviceProvider };
     }
+    const serviceProvider = this.serverless.service.provider;
     service.provider = _.merge(
       {
-        stage: 'dev',
-        region: 'us-east-1',
-        variableSyntax: '\\${([^{}]+?)}',
+        stage: serviceProvider.stage,
+        region: serviceProvider.region,
+        variableSyntax: serviceProvider.variableSyntax,
       },
       service.provider
     );