remove deprectated /shorten API

[nreese]

Do not backport

This PR removes the deprecated /shorten API endpoint from master

[nreese]

@epixa Where is the documentation for breaking changes? Or is the tag release_note:breaking enough?

[elasticmachine]

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[nreese]

fail: "apis xpack_main Settings /api/settings with trial license clusters should load multiple clusters"
22:31:06    │ proc  [ftr]            │       
22:31:06    │ proc  [ftr]            │         Error: expected false to sort of equal true
22:31:06    │ proc  [ftr]            │         + expected - actual
22:31:06    │ proc  [ftr]            │       
22:31:06    │ proc  [ftr]            │         -false
22:31:06    │ proc  [ftr]            │         +true
22:31:06    │ proc  [ftr]            │         
22:31:06    │ proc  [ftr]            │         at Assertion.assert (node_modules/expect.js/index.js:96:13)
22:31:06    │ proc  [ftr]            │         at Assertion.eql (node_modules/expect.js/index.js:230:10)
22:31:06    │ proc  [ftr]            │         at Context.it (test/api_integration/apis/xpack_main/settings/settings.js:37:59)
22:31:06    │ proc  [ftr]            │         at <anonymous>

jenkins, test this

[elasticmachine]

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[elasticmachine]

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[elasticmachine]

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[elasticmachine]

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[chrisdavies]

LGTM. Just code review.