increase node-exporter scrape frequency to allow better data visualization

[paulfantom]

What this PR does / why we need it

With default scrape frequency of 1m, some dashboards show "no data". This is because dashboard queries use $__rate_interval which is dynamically calculated and tuned towards higher scrape frequencies.

Additionally by specifying scrape interval we can get more granular data.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes https://github.com/timescale/sre-monitoring/issues/118

Special notes for your reviewer

Checklist

• [ ] Chart Version bumped
• [ ] CLA signed

[paulfantom]

This should allow to use Node Exporter / Nodes dashboard to visualize volume IOPS data instead of going to AWS console every time.

cc @timescale/o11y-applications