tac: fix crash-loop by installing GNU sed for sed command compatibility

The TAC mainnet container was crash-looping with 'sed: unsupported command ^'
because busybox sed in Alpine does not support the GNU sed extensions used in
the cometbft-common.sh scripts (address ranges with ^ anchor and {} grouping).

Adding the 'sed' package installs GNU sed which supports these features.

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

tac/tacchaind.Dockerfile

@@ -8,7 +8,8 @@ RUN apk upgrade --no-cache && \
     apk add --no-cache \
     ca-certificates \
     curl \
-    libusb
+    libusb \
+    sed
 
 # Download binary and checksums
 ARG VERSION