Change dependabot to weekly instead of daily (#910)

<!--
For the checkboxes below you must check each one to indicate that you
either did the relevant task, or considered it and decided there was
nothing that needed doing
-->

Changing dependabot to weekly instead of daily to reduce noise (mainly
due to that one AWS package that updates damn near every day!).

- [x] Did you write/update appropriate tests
- [x] Release notes updated (if appropriate)
- [x] Appropriate logging output
- [x] Issue linked
- [x] Docs updated (or issue created)
- [x] New package licenses are added to `ThirdPartyNotices.txt` (if
applicable)

<!--
For docs we should review the docs at:

https://docs.github.com/en/early-access/github/migrating-with-github-enterprise-importer
and the README.md in this repo

If a doc update is required based on the changes in this PR, it is
sufficient to create an issue and link to it here. The doc update can be
made later/separately.

The process to update the docs can be found here:
https://github.com/github/docs-early-access#opening-prs

The markdown files are here: 

https://github.com/github/docs-early-access/tree/main/content/github/migrating-with-github-enterprise-importer
-->

Author: dylan-smith

.github/dependabot.yml

@@ -8,4 +8,4 @@ updates:
   - package-ecosystem: "nuget" # See documentation for possible values
     directory: "/" # Location of package manifests
     schedule:
-      interval: "daily"
+      interval: "weekly"