[21.01] Patch to click the button which should be more stable

[hexylena]

What did you do?

• Replaced the now removed Galaxy.upload.show with clicking on the button

Why did you make this change?

This seems to have broken in 21.01, making the 'upload' button in tutorials accessed through this webhook non-functional

How to test the changes?

(select the most appropriate option; if the latter, provide steps for testing below)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. activate the webhook
  2. setup proxying (there's a link at the bottom that appears with documentation on the nginx configuration needed) / setup nginx / etc.
  3. activate webhook
  4. browse to a tutorial that uses the feature (e.g. assembly → the MRSA tutorials)
  5. Click on the blue 'import' button during the first hands-on box
  6. It should open the upload dialogue

License

• I agree to license these contributions under Galaxy's current license.
• I agree to allow the Galaxy committers to license these and all my past contributions to the core galaxy codebase under the MIT license. If this condition is an issue, uncheck and just let us know why with an e-mail to galaxy-committers@lists.galaxyproject.org.

For UI Components

• I've included a screenshot of the changes

[bgruening]

Thanks @hexylena