Remove const keyword when declaring enums

[agubler]

Type: bug

The following has been addressed in the PR:

• There is a related issue
• All code matches the style guide
• Unit or Functional tests are included in the PR

Description:

Removes keyword const from declaring enums.

Resolves #524

[codecov]

Codecov Report

Merging #525 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #525      +/-   ##
=========================================
+ Coverage   97.25%   97.3%   +0.05%     
=========================================
  Files          32      32              
  Lines        2477    2526      +49     
  Branches      642     642              
=========================================
+ Hits         2409    2458      +49     
  Misses          9       9              
  Partials       59      59

Impacted Files	Coverage Δ
src/tooltip/index.ts	100% <100%> (ø)	⬆️
src/split-pane/index.ts	92.78% <100%> (+0.23%)	⬆️
src/tab-controller/index.ts	99.1% <100%> (+0.04%)	⬆️
src/common/util.ts	100% <100%> (ø)	⬆️
src/checkbox/index.ts	96.93% <100%> (+0.09%)	⬆️
src/combobox/index.ts	97.71% <100%> (+0.04%)	⬆️
src/slide-pane/index.ts	89.93% <100%> (+0.57%)	⬆️
src/calendar/DatePicker.ts	99.28% <100%> (+0.03%)	⬆️
... and 5 more

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