fix: add missing await after findPr (#965)

lib/workers/branch/check-existing.js

@@ -14,7 +14,11 @@ async function prAlreadyExisted(config) {
   logger.debug('recreateClosed is false');
   // Return if same PR already existed
   // Check for current PR title format
-  const pr = config.api.findPr(config.branchName, config.prTitle, 'closed');
+  const pr = await config.api.findPr(
+    config.branchName,
+    config.prTitle,
+    'closed'
+  );
   if (pr) {
     logger.debug('Found closed PR with current title');
     // this code exists to ignore mistakenly closed PRs which occurred due to a bug