Deploy to testnet-staging (#337)

## tl;dr

Auto deploy to testnet staging

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Chores**
- Updated the deployment workflow to change the Terraform workspace to
`testnet-staging`.
- Adjusted formatting for consistency in the variable declaration within
the deployment workflow.
- Changed dependency management command from `forge soldeer update` to
`forge soldeer install` in multiple deployment scripts.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/workflows/build-xmtpd.yml

@@ -8,7 +8,6 @@ on:
   workflow_dispatch:
 
 jobs:
-
   push_to_registry:
     strategy:
       matrix:
@@ -70,7 +69,6 @@ jobs:
         id: set_xmtpd_digest
         run: echo "digest=${{ steps.push.outputs.digest }}" >> $GITHUB_OUTPUT
 
-
   deploy:
     name: Deploy new images to infra
     runs-on: ubuntu-latest
@@ -86,7 +84,7 @@ jobs:
           timeout: 45m
           terraform-token: ${{ secrets.TERRAFORM_TOKEN }}
           terraform-org: xmtp
-          terraform-workspace: testnet
+          terraform-workspace: testnet-staging
           variable-name: xmtpd_server_docker_image
           variable-value: "ghcr.io/xmtp/xmtpd@${{ needs.push_to_registry.outputs.xmtpd_digest }}"
-          variable-value-required-prefix: "ghcr.io/xmtp/xmtpd@sha256:"
+          variable-value-required-prefix: "ghcr.io/xmtp/xmtpd@sha256:"

dev/contracts/deploy-ephemeral

@@ -6,6 +6,6 @@ source dev/contracts/.env
 cd ./contracts
 
 # Update depencencies
-forge soldeer update
+forge soldeer install
 
 forge create --legacy --json --broadcast --rpc-url $DOCKER_RPC_URL --private-key $PRIVATE_KEY "$1:$2"

dev/contracts/deploy-local

@@ -11,7 +11,7 @@ mkdir -p ./build
 cd ./contracts
 
 # Update depencencies
-forge soldeer update
+forge soldeer install
 
 # Deploy a contract and save the output (which includes the contract address) to a JSON file to be used in tests
 function deploy_contract() {

dev/contracts/deploy-testnet

@@ -5,7 +5,7 @@ set -euo
 cd ./contracts
 
 # Update depencencies
-forge soldeer update
+forge soldeer install
 
 # Deploy the contract to the chain with the specified RPC URL and attempt to verify the SC code
 function deploy_contract() {