dependabot-2.0: updates[update].groups should not have any required properties

[anentropic]

Removed 'anyOf' requirement for dependency schema.

Fixes: #5685

https://docs.github.com/en/code-security/reference/supply-chain-security/dependabot-options-reference#groups--

• applies-to: "When undefined, defaults to version updates."
• dependency-type: "By default, a group will include all types of dependencies."
• exclude-patterns: implicitly optional, examples are shown without https://docs.github.com/en/code-security/tutorials/secure-your-dependencies/optimizing-pr-creation-version-updates#grouping-updates-across-directories-in-a-monorepo
• group-by: Supported value: dependency-name. "When set to dependency-name, Dependabot will ..."
• patterns: implicitly optional, examples are shown without https://docs.github.com/en/code-security/tutorials/secure-your-dependencies/optimizing-pr-creation-version-updates#grouping-updates-across-directories-in-a-monorepo
• update-types: "By default, a group will include updates for all semantic versions (SemVer)."

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @madskristensen and @hyperupcall - if they write a comment saying "LGTM" then it will be merged.