SNS displayName as optional property when used with topicName

[fredericbarthelet]

Closes: #8294

[codecov-commenter]

Codecov Report

Merging #8323 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #8323   +/-   ##
=======================================
  Coverage   88.02%   88.02%           
=======================================
  Files         249      249           
  Lines        9308     9309    +1     
=======================================
+ Hits         8193     8194    +1     
  Misses       1115     1115           

Impacted Files	Coverage Δ
...ib/plugins/aws/package/compile/events/sns/index.js	100.00% <100.00%> (ø)

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[medikoo]

Thank you @fredericbarthelet !