fix volume statefulset helm chart's tolerations

[theRealWardo]

What problem are we solving?

when trying to set tolerations in the helm chart's values.yaml I received an error

Error: YAML parse error on seaweedfs/templates/volume-statefulset.yaml: error converting YAML to JSON: yaml: line 40: did not find expected key

How are we solving the problem?

the other statefulset templates have correctly intended the tolerations but volume-statefulset.yaml was incorrect

How is the PR tested?

I am now able to set tolerations in my fork of this helm chart 😄

Checks

• I have added unit tests if possible. - not relevant
• I will add related wiki document changes and link to this PR after merging. - not required