minor tweaks to Try Gutenberg callout formatting

[pbiron]

Related: #44611

When the text of the header in the 2nd or 3rd columns of the callout wraps (e.g., with a translation on a narrow screen)

1. the line-height seems to high
   • it currently inherits 2.1 from .try-gutenberg-panel
   • I suggest 1.3, @kjellr suggests 1.4...either works for me
2. the paragraphs do not vertically align
   • while it does not look bad that way, I think it would look better if they did
   • I tried but couldn't figure out how to accomplish that

[pento]

44627.diff​ changes the line height.

It isn't really possible to make the paragraphs vertically align, without significantly reworking the HTML.

As 4.9.8 is in RC, patch needs sign off from another committer.

[afercia]

line-height values should be unitless.

[afercia]

CSS coding standards: ​https://make.wordpress.org/core/handbook/best-practices/coding-standards/css/#values

Line height should also be unit-less, unless necessary to be defined as a specific pixel value. This is more than just a style convention, but is worth mentioning here. More information: ​http://meyerweb.com/eric/thoughts/2006/02/08/unitless-line-heights/

[SergeyBiryukov]

Needs a refresh for a unitless value, looks good to me otherwise (see before/after screenshot above).

[pbiron]

unitless line-height

[pbiron]

see #44643

[pento]

In 43536:

Dashboard: Tweak the "Try Gutenberg" subheading line height.

Props pento, pbiron, afercia, SergeyBiryukov.
Fixes #44627.