Fix false positive for UnusedPrivateMember with expect on objects

[cortinico]

We had a discrepancy on the visitClass and visitClassOrObject method (we were calling the wrong super method). I've fixed this, addressing the expect object scenarios.

Fixes #3415

[codecov]

Codecov Report

Merging #3417 (58a3cff) into master (95a1220) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master    #3417   +/-   ##
=========================================
  Coverage     80.37%   80.37%           
  Complexity     2748     2748           
=========================================
  Files           449      449           
  Lines          8295     8297    +2     
  Branches       1587     1588    +1     
=========================================
+ Hits           6667     6669    +2     
  Misses          774      774           
  Partials        854      854           

Impacted Files	Coverage Δ	Complexity Δ
...turbosch/detekt/rules/style/UnusedPrivateMember.kt	90.76% <100.00%> (+0.14%)	5.00 <0.00> (ø)

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