refactor(deprecations): add info on how to disable

lib/workers/repository/process/deprecated.js

@@ -39,6 +39,8 @@ async function raiseDeprecationWarnings(config, packageFiles) {
       issueBody += `\n\nAffected package file(s): ${depPackageFiles
         .map(f => '`' + f + '`')
         .join(', ')}`;
+      issueBody +=
+        '\n\n Would you like to disable Renovate\'s deprecation warning issues? Add the following to your config:\n\n```\n"suppressNotifications": ["deprecationWarningIssues"]\n```\n\n';
       // istanbul ignore if
       if (config.dryRun) {
         logger.info('DRY-RUN: Ensure deprecation warning issue for ' + depName);