Relax the helm-rg requirement or consider an alternative to helm-rg

[Flowdalic]

The last commit of helm-rg was in summer 2020. That is over three years ago. The project appears unmaintained and issues like https://github.com/cosmicexplorer/helm-rg/issues/39 suggest that it could break in the near future.

Furthermore, helm-rg, as it started to show incomplete results for me. Unfortunately, I was unable to pin point the exact cause, therefore I uninstalled it. However, helm-projectile keeps on asking me to install it again.

Could you please relax helm-projectile's connection to helm-rg? For example, by making it optional. Or use an alternative to helm-rg.