🚑 revert Enketo buttons from <Button>s back to plain HTML

[JGreenlee]

Enketo requires there to be <a> elements with specific IDs for the "next" and "save" buttons. We had nested <Button>s inside these to make them match the <Button>s we use elsewhere in the UI. But in some webviews, the touch events would not bubble up from the <Button> to the <a> elements, causing the buttons to be unclickable except around the margins.

Reverting this back to just use plain <a> elements to resolve the bug. Maybe revisit <Button> later because it was nicer looking.

@shankari

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.49%. Comparing base (78b5da1) to head (79250f7).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1139   +/-   ##
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  Coverage   77.49%   77.49%           
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  Files          29       29           
  Lines        1693     1693           
  Branches      370      370           
=======================================
  Hits         1312     1312           
  Misses        381      381           

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