Rephrase dev mode description to avoid repetition

[shin19991207]

The current description of dev mode says:

When you run Open Liberty in dev mode, dev mode listens for file changes and automatically recompiles and deploys your updates whenever you save a new change.

Avoid repeating "dev mode" and improve the sentence flow, consider rephrasing it as:

When you run Open Liberty in dev mode, it listens for file changes and automatically recompiles and deploys your updates whenever you save a new change.