Fix dependabot config
Apparently the syntax was off (maybe I picked that up from an older
doc?)
It now conforms to
@@ -24,5 +24,5 @@ updates:
# A compatibility layer should come out at some point
# see https://reactrouter.com/docs/en/v6/upgrading/v5
- dependency-name: "react-router-dom"
- update-type: "semver-major"
+ update-types: ["version-update:semver-major"]
