fix: update example external-node docker-compose.yml (#4482)

## What ❔

- update outdated docker-copose.yml

## Why ❔

- old version
- missing gateway url

## Is this a breaking change?
- [ ] Yes
- [x] No

## Operational changes
<!-- Any config changes? Any new flags? Any changes to any scripts? -->
<!-- Please add anything that non-Matter Labs entities running their own
ZK Chain may need to know -->

## Checklist

<!-- Check your PR fulfills the following items. -->
<!-- For draft PRs check the boxes as you complete them. -->

- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [ ] Tests for the changes have been added / updated.
- [x] Documentation comments have been added / updated.
- [ ] Code has been formatted via `zkstack dev fmt` and `zkstack dev
lint`.

Author: cytadela8

docs/src/guides/external-node/docker-compose-examples/mainnet-external-node-docker-compose.yml

@@ -52,7 +52,7 @@ services:
   # Generation of consensus secrets.
   # The secrets are generated iff the secrets file doesn't already exist.
   generate-secrets:
-    image: "matterlabs/external-node:2.0-v28.2.1"
+    image: "matterlabs/external-node:v29.1.2"
     entrypoint:
       [
       "/configs/generate_secrets.sh",
@@ -61,7 +61,7 @@ services:
     volumes:
       - ./configs:/configs
   external-node:
-    image: "matterlabs/external-node:2.0-v28.2.1"
+    image: "matterlabs/external-node:v29.1.2"
     entrypoint:
       [
       "/usr/bin/entrypoint.sh",
@@ -94,6 +94,7 @@ services:
       EN_PROMETHEUS_PORT: 3322
       EN_ETH_CLIENT_URL: https://ethereum-rpc.publicnode.com
       EN_MAIN_NODE_URL: https://zksync2-mainnet.zksync.io
+      EN_GATEWAY_URL: https://rpc.era-gateway-mainnet.zksync.dev
       EN_L1_CHAIN_ID: 1
       EN_L2_CHAIN_ID: 324
       EN_PRUNING_ENABLED: true

docs/src/guides/external-node/docker-compose-examples/testnet-external-node-docker-compose.yml

@@ -52,7 +52,7 @@ services:
   # Generation of consensus secrets.
   # The secrets are generated iff the secrets file doesn't already exist.
   generate-secrets:
-    image: "matterlabs/external-node:2.0-v28.2.1"
+    image: "matterlabs/external-node:v29.1.2"
     entrypoint:
       [
       "/configs/generate_secrets.sh",
@@ -61,7 +61,7 @@ services:
     volumes:
       - ./configs:/configs
   external-node:
-    image: "matterlabs/external-node:2.0-v28.2.1"
+    image: "matterlabs/external-node:v29.1.2"
     entrypoint:
       [
       "/usr/bin/entrypoint.sh",
@@ -94,6 +94,7 @@ services:
       EN_PROMETHEUS_PORT: 3322
       EN_ETH_CLIENT_URL: https://ethereum-sepolia-rpc.publicnode.com
       EN_MAIN_NODE_URL: https://sepolia.era.zksync.dev
+      EN_GATEWAY_URL: https://rpc.era-gateway-testnet.zksync.dev
       EN_L1_CHAIN_ID: 11155111
       EN_L2_CHAIN_ID: 300
       EN_PRUNING_ENABLED: true