Update Dependabot configuration

[smaboshe]

This commit updates the timing of the Dependabot checks. It also updates Dependabot to check for version changes to GitHub Actions.

Ref:

• https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#configuration-options-for-the-dependabotyml-file
• https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#package-ecosystem