Bump to Alpine 3.21 (#156)

Author: agners

build.yaml

@@ -1,10 +1,10 @@
 image: ghcr.io/home-assistant/{arch}-hassio-dns
 build_from:
-  aarch64: ghcr.io/home-assistant/aarch64-base:3.20
-  armhf: ghcr.io/home-assistant/armhf-base:3.20
-  armv7: ghcr.io/home-assistant/armv7-base:3.20
-  amd64: ghcr.io/home-assistant/amd64-base:3.20
-  i386: ghcr.io/home-assistant/i386-base:3.20
+  aarch64: ghcr.io/home-assistant/aarch64-base:3.21
+  armhf: ghcr.io/home-assistant/armhf-base:3.21
+  armv7: ghcr.io/home-assistant/armv7-base:3.21
+  amd64: ghcr.io/home-assistant/amd64-base:3.21
+  i386: ghcr.io/home-assistant/i386-base:3.21
 codenotary:
   signer: notary@home-assistant.io
   base_image: notary@home-assistant.io