Cleanup usage of .fetchLabelPages() as page number isn't needed anymore

In 4164d9e `.fetchLabelPages()` got
simplified to use the built-in pagination of oktokit. That resulted in
the using code no longer having to provide the page number wanting to be
fetched.

lib/node-repo.js

@@ -82,7 +82,7 @@ async function fetchExistingLabels (options) {
     return existingLabelsCache.get(cacheKey)
   }
 
-  const labelsResult = await fetchLabelPages(options, 1)
+  const labelsResult = await fetchLabelPages(options)
   const existingLabels = labelsResult.data || labelsResult || []
   const existingLabelNames = existingLabels.map((label) => label.name)