Replace Twitter embed with Markdown blockquote in development principles

- [Frontend Guides](https://docs.gitlab.com/ee/development/fe_guide/index.html)

- [Database Guides](https://docs.gitlab.com/ee/development/#database-guides)

Please remember that the only way to make code flexible is to make it as simple as possible:

Please remember that the only way to make code flexible is to make it as simple as possible.

<blockquote class="twitter-tweet" data-lang="en"><p lang="en" dir="ltr">A lot of programmers make the mistake of thinking the way you make code flexible is by predicting as many future uses as possible, but this paradoxically leads to *less* flexible code.<br>

The only way to achieve flexibility is to make things as simple and easy to change as you can.</p>&mdash; Nearby Cats (@BaseCase) <a href="https://twitter.com/BaseCase/status/1085686616499183616?ref_src=twsrc%5Etfw">January 16, 2019</a></blockquote>

<script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>

[Nearby Cats (@BaseCase)](https://twitter.com/BaseCase/status/1085686616499183616) wrote on January 16, 2019:

> A lot of programmers make the mistake of thinking the way you make code flexible is by predicting as many future uses as possible, but this paradoxically leads to *less* flexible code.

> The only way to achieve flexibility is to make things as simple and easy to change as you can.

### UI consistency and maintainability across Rails and VueJS Frontend