Update upstream repo for rules_shell

[Wyverald]

rules_shell was moved to bazel-contrib. You'd think having a redirect left behind would be fine, but we keep getting emails about "commit status have been disabled for rules_shell". Let's see if updating the repo fixes it.

[github-actions]

Terraform Plan for bazel 📖

Plan: 0 to add, 1 to change, 0 to destroy.

Show Plan

Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
  ~ update in-place

Terraform will perform the following actions:

  # buildkite_pipeline.rules-shell will be updated in-place
  ~ resource "buildkite_pipeline" "rules-shell" {
      + cluster_name                             = (known after apply)
        id                                       = "UGlwZWxpbmUtLS0wMTkyNTdkMC04OGU3LTRmNDQtYTJiOS1lNzRkYjI3ZjJkYTQ="
        name                                     = "rules_shell"
      ~ provider_settings                        = {
          ~ publish_blocked_as_pending                    = true -> false
          ~ publish_commit_status                         = false -> true
            # (22 unchanged attributes hidden)
        }
      ~ repository                               = "https://github.com/bazelbuild/rules_shell.git" -> "https://github.com/bazel-contrib/rules_shell.git"
      ~ slug                                     = "rules-shell" -> (known after apply)
        tags                                     = []
        # (12 unchanged attributes hidden)
    }

Plan: 0 to add, 1 to change, 0 to destroy.