[Fix] jsx-no-literals: Avoid crashing on valueless boolean props

[reosarevok]

b8217ed removed the node.value check leading to this crashing on any valueless boolean prop such as <Component isWhatever />

This just readds the check.

Fixes #3820

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.66%. Comparing base (a09083b) to head (99e15e1).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3823      +/-   ##
==========================================
+ Coverage   95.97%   97.66%   +1.68%     
==========================================
  Files         136      133       -3     
  Lines        9929     9917      -12     
  Branches     3677     3678       +1     
==========================================
+ Hits         9529     9685     +156     
+ Misses        400      232     -168     

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[ljharb]

Thanks!