Update rattler pin (regularly)

The discussion in https://github.com/conda/rattler/issues/2023 etc. lead to the statement that rattler still needs to evolve its API and that we should pin to the minor version: https://github.com/conda-forge/conda-smithy/blob/c771d9b52815e29bf5f52bebf502c085b3d62147/environment.yml#L42-L43 That freedom to evolve is fair enough, but given that rattler-build is taking on an ever-more fundamental role in conda-forge, someone needs to do the maintenance that follows from API changes. IMO, the most obvious party for this would be the rattler developers, who IMO should update smithy to be compatible with each new rattler release (which may be as simple as lifting the version cap). This hasn't happened for a while, and carrying that cap will lead us into problems eventually. CC @baszalmstra @wolfv @pavelzw