fix(dropdown): fix bottom position for dropdownlist

[ghost]

Closes to #4545
it fixed dropdown list bottom position. If the user is using bootstrap 4, directive adds transform style, and bottom style (bottom: 100%) is redundant

[codecov]

Codecov Report

Merging #4626 into development will increase coverage by 0.14%.
The diff coverage is 100%.

@@               Coverage Diff               @@
##           development    #4626      +/-   ##
===============================================
+ Coverage         74.7%   74.85%   +0.14%     
===============================================
  Files              276      276              
  Lines             8385     8390       +5     
  Branches          1594     1594              
===============================================
+ Hits              6264     6280      +16     
+ Misses            1682     1670      -12     
- Partials           439      440       +1

Impacted Files	Coverage Δ
src/dropdown/bs-dropdown.directive.ts	85.92% <100%> (+6.97%)	⬆️
src/datepicker/reducer/bs-datepicker.effects.ts	72.47% <0%> (-1.84%)	⬇️
src/tooltip/tooltip-container.component.ts	76.47% <0%> (ø)	⬆️
src/typeahead/typeahead.directive.ts	74.86% <0%> (+1.04%)	⬆️
src/tooltip/tooltip.directive.ts	60% <0%> (+1.12%)	⬆️
src/datepicker/engine/flag-days-calendar.ts	80% <0%> (+6.66%)	⬆️

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[Domainv]

code coverage test

[ludmilanesvitiy]

Dropdowns demo tested in CHrome, FF - looks good.