chore: release-please config for 21.8 (#712)
chore: release-please config for 21.8 (#712)

includes setting packages/sdk-* to whatever their next version should be
looker-open-source/sdk-codegen,looker-open-source/sdk-codegen,looker-open-source/sdk-codegen,looker-open-source/sdk-codegen,looker-open-source/sdk-codegen,looker-open-source/sdk-codegen,looker-open-source/sdk-codegen,looker-open-source/sdk-codegen,looker-open-source/sdk-codegen