[Improvement]: Fix deprecation inside default devcontainer

[Shadow-Devil]

Description

Describe your problem(s)

No response

Describe your solution(s)

Change the default template to this:

{
    "image": "ballerina/ballerina-devcontainer:latest",
    "customizations":{
        "vscode": {
            "extensions": ["WSO2.ballerina"]
        }
    }
}

Related area

-> Other Area

Related issue(s) (optional)

32546

Suggested label(s) (optional)

No response

Suggested assignee(s) (optional)

I would like to contribute myself