Use matching version of @tiptap/core

--- a/package.json
+++ b/package.json
@@ -65,7 +65,7 @@
     "@rails/ujs": "6.1.3-2",
     "@sentry/browser": "5.26.0",
     "@sourcegraph/code-host-integration": "0.0.59",
-    "@tiptap/core": "^2.0.0-beta.86",
+    "@tiptap/core": "2.0.0-beta.86",
     "@tiptap/extension-blockquote": "^2.0.0-beta.14",
     "@tiptap/extension-bold": "^2.0.0-beta.14",
     "@tiptap/extension-bullet-list": "^2.0.0-beta.14",