Update memcached

Changes:

- https://github.com/docker-library/memcached/commit/4538128: Update to 1.6.6
- https://github.com/docker-library/memcached/commit/8c08158: Merge pull request https://github.com/docker-library/memcached/pull/58 from docker-library/github-actions
- https://github.com/docker-library/memcached/commit/3b8a264: Add initial GitHub Actions CI

library/memcached

@@ -4,12 +4,12 @@ Maintainers: Tianon Gravi <[email protected]> (@tianon),
              Joseph Ferguson <[email protected]> (@yosifkit)
 GitRepo: https://github.com/docker-library/memcached.git
 
-Tags: 1.6.5, 1.6, 1, latest
+Tags: 1.6.6, 1.6, 1, latest
 Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, mips64le, ppc64le, s390x
-GitCommit: 54f0aa6b002c2849425505dce9a344dd98417263
+GitCommit: 4538128227a0e422e59df735d67b03ee23d39637
 Directory: debian
 
-Tags: 1.6.5-alpine, 1.6-alpine, 1-alpine, alpine
+Tags: 1.6.6-alpine, 1.6-alpine, 1-alpine, alpine
 Architectures: amd64, arm32v6, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: 54f0aa6b002c2849425505dce9a344dd98417263
+GitCommit: 4538128227a0e422e59df735d67b03ee23d39637
 Directory: alpine