Remove WordPress.com tour banner from view in UBE

[SiobhyB]

Fixes #4079

What?

This PR removes the WordPress.com tour banner that sometimes pops up when opening the unsupported block editor (UBE).

Before	After

Note, the cookie banner remains as I'm assuming it'd be necessary to get the thumbs up from legal before hiding it and it's not as disruptive as the tour banner.

Why?

The tour banner is specific to the web version of the editor, it's therefore confusing and distracting within the UBE.

How?

Previously, as part of the changes in #4352, the external-style-overrides.css file was created for the purpose of "housing" CSS that didn't belong in the Gutenberg repository. It has a Gutenberg equivalent here.

Following the approach we've taken to hide other elements in the UBE, this PR adds CSS to the external-style-overrides.css that targets the tour banner and hides it from view.

Testing Instructions

This may be only reproducible on a new WordPress.com site, since the popup might only be shown once.

1. Locate a post that contains an unsupported block (e.g. Calendar at time of writing)
2. Open the post and expect to see the block rendered as a placeholder with the text "Unsupported"
3. Tap the (?) icon and expect the option to edit the block in a web browser to be shown
4. Tap the edit in a web browser button and expect the block to be shown, confirm that the "Welcome to WordPress!" banner is no longer visible

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PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes more info and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

Wanna run full suite of Android and iOS UI tests? Click here and 'Approve' CI job!

[mchowning]

👋 @SiobhyB ! I'm having some trouble testing this. When I create a new free WordPress.com site, I'm not seeing any "Welcome to WordPress" banner either on the web when I start a new post or in the app (without the changes from this PR applied) when I edit an unsupported block. I know I've seen it before, but I don't know if there's something I'm doing wrong now to keep it from showing up. Any ideas?

[SiobhyB]

Thanks for taking a look at this, @mchowning! I did some digging and found there's an option to enable the Welcome Guide under the editor's settings on the web:

I think if you enable it there, you should then be able to see it within the UBE on the app. Would you be able to give that a try to see if it works for you?

[mchowning]

Thanks for this fix @SiobhyB . I updated the gb-mobile reference in WPAndroid and saw that this change works perfectly.

If I use metro though (instead of the bundle), then the display property doesn't get applied and the popup still appears. I'm not sure exactly why that is, but I noticed you had to make a tweak to get this to work in the bundle—maybe that made it so that it didn't work in metro? Anyway, I'll go ahead and approve since it is the bundle that is the most important. If there were a way to get this to work both with metro and the bundle that would be great though.

[SiobhyB]

Thanks @mchowning! 🙌

If I use metro though (instead of the bundle), then the display property doesn't get applied and the popup still appears.

I only able to get the fix working with metro if I restarted the activity and re-ran the app in Android, it didn't automatically update like other changes to Gutenberg do (I think that's expected with UBE changes). Perhaps that's related? I'll go ahead to merge the PR as I believe it will work as expected with metro with a fresh install/restart. Let me know if there's still problems that I'm missing, though.