chore(getElementType): remove unused logic branches

[kuzhelov]

This PR removes couple of branches from logic of getElementType method that infers element type for rendered Stardust component.

One of these branches - getDefault, - wasn't used anywhere, while another one provides unnecessary complication to element type's inference.

BREAKING CHANGES

These changes are NOT breaking for clients that are using Typescript, as well as highly likely to introduce no breaking changes to JS clients, given that they are affecting edge-case usages.

The following elements that were originally rendered as a now will be rendered as as or default element of the corresponding component:

// - was rendered as <a href>{content}</a> 
// - now is rendered as <span href>{content}</span> 
<Text href='..' content={...} />  

Migration path

It is necessary to provide value for as prop explicitly:

<Text as='a' href='..' content={...} /> 

[miroslavstastny]

👍 on code changes.
But as this functionality goes back to SUIR, it might be useful to hear @levithomason opinion.

[codecov]

Codecov Report

Merging #1396 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1396      +/-   ##
==========================================
+ Coverage   73.47%   73.49%   +0.01%     
==========================================
  Files         778      778              
  Lines        5859     5855       -4     
  Branches     1726     1723       -3     
==========================================
- Hits         4305     4303       -2     
+ Misses       1548     1546       -2     
  Partials        6        6

Impacted Files	Coverage Δ
packages/react/src/lib/getElementType.tsx	100% <100%> (+25%)	⬆️

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[codecov]

Codecov Report

Merging #1396 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1396      +/-   ##
==========================================
+ Coverage   73.49%   73.51%   +0.01%     
==========================================
  Files         786      786              
  Lines        5867     5863       -4     
  Branches     1706     1723      +17     
==========================================
- Hits         4312     4310       -2     
+ Misses       1549     1547       -2     
  Partials        6        6

Impacted Files	Coverage Δ
packages/react/src/lib/getElementType.tsx	100% <100%> (+25%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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