We were having a minor issue with emails with embedded images
that had newlines in the alt string; for example:
```
<p class="MsoNormal"><span style="font-size:11.0pt"><img width="898"
height="498" style="width:9.3541in;height:5.1875in" id="Picture_x0020_5"
src="cid:image003.png@01DA4EBA.0400B610" alt="A screenshot of a computer
program
Description automatically generated"></span><span
style="font-size:11.0pt"><o:p></o:p></span></p>
```
Once this was parsed and converted to markdown (or directly to HTML
in some cases), this caused an issue in the composer and the post
UI, where the markdown parser didn't know how to deal with this,
making the HTML show directly instead of showing an image.
The easiest way to deal with this is to just strip \n from image
alt and title attrs in the HTMLToMarkdown class.
It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
