Fieldset - Remove bottom margin if wrapping a h1

[boxadesign]

What is the context of this PR?

Remove bottom margin if fieldset is wrapping a h1 (using parameter legendIsQuestionTitle).

[codecov]

Codecov Report

Merging #1783 (b35220f) into master (ddb05cc) will increase coverage by 0.09%.
The diff coverage is 96.95%.

@@            Coverage Diff             @@
##           master    #1783      +/-   ##
==========================================
+ Coverage   96.39%   96.49%   +0.09%     
==========================================
  Files          65       69       +4     
  Lines        2746     3107     +361     
==========================================
+ Hits         2647     2998     +351     
- Misses         99      109      +10     

Impacted Files	Coverage Δ
src/components/timeout-modal/timeout.js	92.96% <92.96%> (ø)
src/tests/spec/modal/modal.spec.js	98.41% <98.41%> (ø)
src/tests/spec/timeout-modal/timeout-modal.spec.js	99.18% <99.18%> (ø)
src/components/modal/modal.js	100.00% <100.00%> (ø)
src/components/tabs/tabs.js	91.24% <0.00%> (+0.72%)	⬆️

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