Trim multiline text in warnings

[petertrr]

What's done:

• Changed logic in Warnings.kt

This pull request closes #257

[codecov]

Codecov Report

Merging #322 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #322      +/-   ##
============================================
+ Coverage     82.36%   82.38%   +0.02%     
- Complexity      999     1000       +1     
============================================
  Files            51       51              
  Lines          2575     2578       +3     
  Branches        808      809       +1     
============================================
+ Hits           2121     2124       +3     
  Misses          169      169              
  Partials        285      285              

Flag	Coverage Δ	Complexity Δ
#unittests	82.38% <100.00%> (+0.02%)	1000.00 <0.00> (+1.00)

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Impacted Files	Coverage Δ	Complexity Δ
...tlin/org/cqfn/diktat/ruleset/constants/Warnings.kt	96.66% <100.00%> (+0.11%)	9.00 <0.00> (+1.00)

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[kentr0w]

LGTM