Fix Dependabot pull requests limit (#2017)

There seems to be a bug in the backend that thinks we're hitting the default limit of 5 even when no PRs are open.

Also switch to weekly like the client.

Author: andyleejordan

.github/dependabot.yml

@@ -3,8 +3,9 @@ updates:
 - package-ecosystem: nuget
   directory: "/"
   schedule:
-    interval: daily
+    interval: weekly
+  open-pull-requests-limit: 10
 - package-ecosystem: github-actions
   directory: "/"
   schedule:
-      interval: daily
+    interval: weekly