fixed time and date picker overlay issue

[shreekeshmurkar]

Fixed following issue of date and time select overlay: https://github.com/Hacker0x01/react-datepicker/issues/3588

Before fix:

After fix:

[codecov[bot]]

Codecov Report

Merging #3668 (6f42618) into master (1d84d31) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3668   +/-   ##
=======================================
  Coverage   93.34%   93.34%           
=======================================
  Files          20       20           
  Lines        1352     1352           
  Branches      377      377           
=======================================
  Hits         1262     1262           
  Misses         27       27           
  Partials       63       63           

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[shreekeshmurkar]

@martijnrusschen Please review