[MINOR] Fix broken CSS for plain text paragraph result

[AhyoungRyu]

What is this PR for?

After #1711 merged, plain text paragraph result CSS is broken now. Originally the text result like below (it's 0.6.2). The font was Monaco applied by .paragraph .text class.

But now bootstrap default font Helvetica is used.

So I bring it back by adding new class .plainTextContainer.

What type of PR is it?

Bug Fix

What is the Jira issue?

No Jira issue for this

How should this be tested?

1. See the current text paragraph result (e.g. Zeppelin tutorial: Spark)
2. Apply this patch and start dev mode under zeppelin-web \w npm run dev -> browse http://localhost:9000
3. Compare the text paragraph result

Screenshots (if appropriate)

Questions:

• Does the licenses files need update? no
• Is there breaking changes for older versions? no
• Does this needs documentation? no

[soralee]

@AhyoungRyu What a nice catch!
Tested and It works very well 👍

[Before]

[After]

[AhyoungRyu]

@soralee Thanks for testing it out!

[AhyoungRyu]

Merge if there are no more comments on this