Added test cases for semantic version check

[jadhavmanoj]

Issue #891, if available:

Description of changes:
Added test cases for semantic version check (if provided as None/Empty)

Description of how you validated changes:

Checklist:

• Write/update tests
• make pr passes
• Update documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #929 into develop will increase coverage by 0.06%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #929      +/-   ##
===========================================
+ Coverage    94.66%   94.73%   +0.06%     
===========================================
  Files           69       69              
  Lines         3018     3018              
  Branches       562      562              
===========================================
+ Hits          2857     2859       +2     
+ Misses          85       84       -1     
+ Partials        76       75       -1

Impacted Files	Coverage Δ
...lator/plugins/application/serverless_app_plugin.py	83.44% <0%> (+1.32%)	⬆️

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[keetonian]

Looks good! Thanks!