[Docs] jsx-no-useless-fragment: add more examples of correct code

[karlhorky]

Hey @ljharb ! 👋

Just a quick PR to:

1. Add some simpler examples of how to resolve the react/jsx-no-useless-fragment problems when they appear (there are not as many simple examples of just removing the fragment when there's a single child)
2. Add an example with an embedded expression and ternary

[codecov]

Codecov Report

Merging #3349 (9ffd3b5) into master (7302a2a) will decrease coverage by 0.00%.
The diff coverage is n/a.

❗ Current head 9ffd3b5 differs from pull request most recent head ab72e48. Consider uploading reports for the commit ab72e48 to get more accurate results

@@            Coverage Diff             @@
##           master    #3349      +/-   ##
==========================================
- Coverage   97.71%   97.71%   -0.01%     
==========================================
  Files         123      123              
  Lines        8790     8788       -2     
  Branches     3191     3190       -1     
==========================================
- Hits         8589     8587       -2     
  Misses        201      201              

Impacted Files	Coverage Δ
lib/rules/require-default-props.js	100.00% <0.00%> (ø)

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[karlhorky]

Thanks for the review and merge!