Fix maru version: v1.2.0 -> v1.2.1-20260410142843-d326b73

v1.2.0 tag doesn't exist on Docker Hub, causing compose build
failures on de-27, de-32, us-40. Using the actual tag format.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

op/geth/hashkeychain-testnet-op-geth-pruned-pebble-path.yml

@@ -55,7 +55,7 @@ services:
     environment:
       - GETH_OP_NETWORK=hashkeychain-testnet
       - GETH_ROLLUP_DISABLETXPOOLGOSSIP=true
-      - GETH_ROLLUP_SEQUENCERHTTP=https://testnet.hsk.xyz
+      - GETH_ROLLUP_SEQUENCERHTTP=https://hashkeychain-testnet.alt.technology
     entrypoint: /bin/sh -c 'exec geth "$@"' --
     command:
       - --datadir=/data