Remove redundant newline in Development section of Docs

[domlimm]

Steps to reproduce

Production/Live

1. Visit https://teammates.github.io/teammates/development.html#pre-requisites.

Locally

1. Change directory into the docs folder in project root i.e., cd docs.
2. Run npm run serve.
3. Visit http://127.0.0.1:8080/teammates/development.html#managing-the-dev-server-back-end.

Expected behaviour

Line 2 should be removed. Not sure why the line numbers are not showing locally, please disregard that.

Actual behaviour

[github-actions]

Good First Issue - Notes for Contributors
This issue is for first-time contributors only. If you are new to TEAMMATES, feel free to submit a PR for this issue.

Please note that we allow only one good first issue per contributor. If you have already made a prior contribution to TEAMMATES, you may wish to take a look at issues with the help wanted tag instead.

We do not assign issues to contributors. If you would like to pick up this issue, do post a comment below to express your interest and check if there is anyone else who is already working on the issue. We will do our best to reply and give you the go-ahead, but if we don't, feel free to submit a PR as long as there is no one else working on it.

To get started, do read through our contributing guidelines carefully, and set up a development environment on your local machine before making a PR.

If you need any clarifications on our developer guide, or are facing issues that are not found in our troubleshooting guide, please post a message in our discussion forum.

[pushkarkohli1]

planning to work on #12671