Update bash

Changes:

- https://github.com/tianon/docker-bash/commit/dfb58fd: Update to commit c6c7ae81bb0db03acb1085ac4692934856bf7302
- https://github.com/tianon/docker-bash/commit/daf760c: Update GitHub Actions from "actions/checkout@v1" to "v2"
- https://github.com/tianon/docker-bash/commit/9cd99b2: Update GITHUB_REPOSITORY to bash so images get tagged/tested properly
- https://github.com/tianon/docker-bash/commit/7629122: Update update.sh
- https://github.com/tianon/docker-bash/commit/7def184: Update README stub
- https://github.com/tianon/docker-bash/commit/6c29dea: Merge pull request https://github.com/tianon/docker-bash/pull/20 from tianon/github-actions
- https://github.com/tianon/docker-bash/commit/9696772: Add initial GitHub Actions CI
- https://github.com/tianon/docker-bash/commit/fd17246: Update to commit 69333f10bbd56ba9f93c87d939569aa12d9b24f1
- https://github.com/tianon/docker-bash/commit/388be2a: Update to commit 7910c04f143976600f0699f606818b38fe25b55e

library/bash

@@ -3,9 +3,9 @@
 Maintainers: Tianon Gravi <[email protected]> (@tianon)
 GitRepo: https://github.com/tianon/docker-bash.git
 
-Tags: devel-20200420, devel
+Tags: devel-20200427, devel
 Architectures: amd64, arm32v6, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: 6cdcb0aa849830fbd64d6784c5dde58d1d79f20a
+GitCommit: dfb58fdfa2b8af7a5d3b832dc875a8660f154fe3
 Directory: devel
 
 Tags: 5.0.17, 5.0, 5, latest