Try skipping Dependabot updates on benchmarks

[emmatyping]

Wanted to see if this might skip the benchmark dependencies which we want to keep stable.

See #223 for context.

[hugovk]

I'm not sure if this config file applies to the Dependabot security related PRs?

Anyway, I pushed this to my fork's main and it gives an error:

Your .github/dependabot.yml contained invalid details

Dependabot encountered the following error when parsing your .github/dependabot.yml:

The property '#/updates/1/directories' of type string did not match the following type: array

Please update the config file to conform with Dependabot's specification.

For more info on the config file format, see the config file documentation

https://github.com/hugovk/pyperformance/runs/42703898168

[emmatyping]

I fixed the syntax on my fork but it still didn't work :(

[hugovk]

Thanks anyway for giving it a shot.