chore: fix syntax error in_docker variable (#41041)

## Description
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Fixes #`Issue Number`  
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Fixes `Issue URL`
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## Automation

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### 🔍 Cypress test results
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> <hr>Wed, 25 Jun 2025 13:11:28 UTC
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## Communication
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

- **Bug Fixes**
- Corrected formatting and quoting issues in the deployment script to
ensure proper environment variable expansion and configuration output.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: pratapaprasanna

scripts/deploy_preview.sh

@@ -15,7 +15,7 @@ export cluster_name=uatx-cluster
 
 echo "[default]
 region = $region
-output = json
+output = json"
 
 echo "Region: $region"
 echo "Cluster name: $cluster_name"
@@ -105,6 +105,6 @@ helm upgrade -i "$CHARTNAME" "appsmith-ee/$HELMCHART" -n "$NAMESPACE" --create-n
   --set applicationConfig.APPSMITH_CARBON_API_KEY="$APPSMITH_CARBON_API_KEY" \
   --set applicationConfig.APPSMITH_CARBON_API_BASE_PATH="$APPSMITH_CARBON_API_BASE_PATH" \
   --set applicationConfig.APPSMITH_AI_SERVER_MANAGED_HOSTING="$APPSMITH_AI_SERVER_MANAGED_HOSTING" \
-  --set applicationConfig.IN_DOCKER='$IN_DOCKER' \
+  --set applicationConfig.IN_DOCKER="$IN_DOCKER" \
   --set applicationConfig.APPSMITH_CUSTOMER_PORTAL_URL="https://release-customer.appsmith.com" \
   -f dp-node-affinity-values.yaml