fixed Travis

[StrikerRUS]

Checklist

• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the [Contribution Guide] and my PR follows them.
• I updated my branch with the master branch.
• I have added tests that prove my fix is effective or that my feature works
• [n/a] I have added necessary documentation about the functionality in the appropriate .md file
• [n/a] I have added in line documentation to the code I modified

Short description of what this PR does:

• remove test for checking the existence of USE_CASES.md file, since there is no such file in the repo.

PS. Codecov should be fixed after this PR too.

[SendGridDX]

All committers have signed the CLA.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@ee2b073). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             master     #74   +/-   ##
========================================
  Coverage          ?   99.3%           
========================================
  Files             ?       2           
  Lines             ?     144           
  Branches          ?       0           
========================================
  Hits              ?     143           
  Misses            ?       1           
  Partials          ?       0

Impacted Files	Coverage Δ
test/__init__.py	100% <ø> (ø)

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[StrikerRUS]

Suppressed by #75.