fix bug when dynamically change format

[leochen0818]

It should get new list of hour when format be changed.

[codecov]

Codecov Report

Merging #167 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #167      +/-   ##
==========================================
+ Coverage   98.78%   98.78%   +<.01%     
==========================================
  Files          32       32              
  Lines         657      658       +1     
  Branches      131      131              
==========================================
+ Hits          649      650       +1     
  Partials        8        8

Impacted Files	Coverage Δ
...timepicker-field/ngx-timepicker-field.component.ts	100% <100%> (ø)	⬆️

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