Update memcached

Changes:

- https://github.com/docker-library/memcached/commit/99a2186: Update 1 to alpine 3.21

library/memcached

@@ -9,7 +9,7 @@ Architectures: amd64, arm32v5, arm64v8, i386, mips64le, ppc64le, s390x
 GitCommit: d2fb263f47fa4043f4fe5a207c19517585867592
 Directory: 1/debian
 
-Tags: 1.6.33-alpine, 1.6-alpine, 1-alpine, alpine, 1.6.33-alpine3.20, 1.6-alpine3.20, 1-alpine3.20, alpine3.20
+Tags: 1.6.33-alpine, 1.6-alpine, 1-alpine, alpine, 1.6.33-alpine3.21, 1.6-alpine3.21, 1-alpine3.21, alpine3.21
 Architectures: amd64, arm64v8, i386, ppc64le, riscv64, s390x
-GitCommit: d2fb263f47fa4043f4fe5a207c19517585867592
+GitCommit: 99a2186f3db3de537ea36046164c302d076ac2c4
 Directory: 1/alpine