Update ruby

Changes:

- https://github.com/docker-library/ruby/commit/0555f85: Merge pull request https://github.com/docker-library/ruby/pull/326 from sdwolfz/ruby-3
- https://github.com/docker-library/ruby/commit/57a8df4: Add ruby 3.0.0-preview1

library/ruby

@@ -4,6 +4,21 @@ Maintainers: Tianon Gravi <[email protected]> (@tianon),
              Joseph Ferguson <[email protected]> (@yosifkit)
 GitRepo: https://github.com/docker-library/ruby.git
 
+Tags: 3.0.0-preview1-buster, 3.0-rc-buster, 3.0.0-preview1, 3.0-rc
+Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
+GitCommit: 57a8df4f141840757a74c6caf8d8bae7010cc512
+Directory: 3.0-rc/buster
+
+Tags: 3.0.0-preview1-slim-buster, 3.0-rc-slim-buster, 3.0.0-preview1-slim, 3.0-rc-slim
+Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
+GitCommit: 57a8df4f141840757a74c6caf8d8bae7010cc512
+Directory: 3.0-rc/buster/slim
+
+Tags: 3.0.0-preview1-alpine3.12, 3.0-rc-alpine3.12, 3.0.0-preview1-alpine, 3.0-rc-alpine
+Architectures: amd64, arm32v6, arm32v7, arm64v8, i386, ppc64le, s390x
+GitCommit: 57a8df4f141840757a74c6caf8d8bae7010cc512
+Directory: 3.0-rc/alpine3.12
+
 Tags: 2.7.1-buster, 2.7-buster, 2-buster, buster, 2.7.1, 2.7, 2, latest
 Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
 GitCommit: 8e49e25b591d4cfa6324b6dada4f16629a1e51ce
@@ -35,12 +50,12 @@ GitCommit: 8e49e25b591d4cfa6324b6dada4f16629a1e51ce
 Directory: 2.6/buster/slim
 
 Tags: 2.6.6-stretch, 2.6-stretch
-Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
+Architectures: amd64, arm32v5, arm32v7, arm64v8, i386
 GitCommit: 8e49e25b591d4cfa6324b6dada4f16629a1e51ce
 Directory: 2.6/stretch
 
 Tags: 2.6.6-slim-stretch, 2.6-slim-stretch
-Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
+Architectures: amd64, arm32v5, arm32v7, arm64v8, i386
 GitCommit: 8e49e25b591d4cfa6324b6dada4f16629a1e51ce
 Directory: 2.6/stretch/slim
 
@@ -65,12 +80,12 @@ GitCommit: 8e49e25b591d4cfa6324b6dada4f16629a1e51ce
 Directory: 2.5/buster/slim
 
 Tags: 2.5.8-stretch, 2.5-stretch
-Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
+Architectures: amd64, arm32v5, arm32v7, arm64v8, i386
 GitCommit: 8e49e25b591d4cfa6324b6dada4f16629a1e51ce
 Directory: 2.5/stretch
 
 Tags: 2.5.8-slim-stretch, 2.5-slim-stretch
-Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
+Architectures: amd64, arm32v5, arm32v7, arm64v8, i386
 GitCommit: 8e49e25b591d4cfa6324b6dada4f16629a1e51ce
 Directory: 2.5/stretch/slim