Chore: Update actions to use node 20

[ashharrison90]

No description provided.

[baldm0mma]

Any worries this dep update will create any unforeseen issues? 4 major versions seem like a big jump! 🤔

[ashharrison90]

Any worries this dep update will create any unforeseen issues? 4 major versions seem like a big jump! 🤔

naw not really 😅 couple of reasons:

• node has a slightly weird versioning strategy where every even version is their stable new major version, so it's kinda only 2 major versions
• node is pretty stable. this was the amount of changes needed for the whole of grafana/grafana to move to node 20: Chore: Update to node 20 grafana#76097. i would expect these actions to be even more likely to just work.