turning off build comments on PRs (#1327)

/cc @BillWagner

Author: mairaw

.openpublishing.publish.config.json

@@ -1,7 +1,8 @@
 {
     "need_generate_pdf": false,
     "need_generate_intellisense": false,
-    "need_preview_pull_request": "true",
+    "need_preview_pull_request": true,
+    "need_pr_comments": false,
     "need_generate_pdf_url_template": true,
     "git_repository_branch_open_to_public_contributors": "master",
     "git_repository_url_open_to_public_contributors": "https://github.com/dotnet/core-docs",