fix(thanos): set proper resources defaults

[sjentzschsap]

Submit a pull request

Thank you for submitting a pull request!
To speed up the review process, please ensure that everything below
is true:

1. This is not a duplicate of an existing Plugin.
2. No existing features have been broken without good reason.
3. The Documentation has been updated to reflect your changes.
4. Tests have been added or updated to reflect your changes.
5. All tests pass.

---

Replace any ":question:" below with information about your pull request.

Pull Request Details

Provide details about your pull request and what it adds, fixes, or changes.

Set resources properly to an empty struct instead of null, which fixes a strict deployment where this e.g. does not not allow us to set requests without also defining limits (error: Invalid value: “500m”: must be less than or equal to cpu limit of 0,).

Breaking Changes

Describe what features are broken by this pull request and why, if any.

none

Issues Fixed

Enter the issue numbers resolved by this pull request below, if any.

Other Relevant Information

Provide any other important details below.