Added flaky as a dependency for running tests

[PritishSehzpaul]

Context: Flaky was missing as a required dependency from the doc. Without it make test fails.

Description of the Change: Added flaky as a dependency in the doc and why it is required.

Benefits: Better, more complete documentation.

Possible Drawbacks: None.

Related GitHub Issues: #1099

[codecov]

Codecov Report

Merging #1113 (eb4db57) into master (13aead4) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1113   +/-   ##
=======================================
  Coverage   97.73%   97.74%           
=======================================
  Files         155      155           
  Lines       11760    11760           
=======================================
+ Hits        11494    11495    +1     
+ Misses        266      265    -1     

Impacted Files	Coverage Δ
pennylane/circuit_graph.py	98.69% <0.00%> (+0.43%)	⬆️

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[josh146]

Thanks @PritishSehzpaul for this contribution! Just left a comment regarding the contributor name ordering in the changelog, but apart from that it looks great and should be ready for merging directly after 🙂

[josh146]

Hi @PritishSehzpaul, a recent commit to master corrected the alphabetical ordering of contributors, so this should be good to merge in now. Thanks for the contribution!