SF-3331b Simplify CSS for multi book selection

[Nateowami]

• Simplifies the CSS a bit
• Fixes the layout on small screens when deuterocanon is shown

Before	After

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This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.92%. Comparing base (0786458) to head (82e63c8).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3214   +/-   ##
=======================================
  Coverage   81.92%   81.92%           
=======================================
  Files         604      604           
  Lines       34656    34656           
  Branches     5614     5597   -17     
=======================================
  Hits        28392    28392           
- Misses       5426     5438   +12     
+ Partials      838      826   -12     

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[josephmyers]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Nateowami)