Enable Zendesk tickets from Automatticians

[nbradbury]

Fixes #21449

Automatticians who have a Zendesk staff member role (admin, agent, etc.) identity have long been unable to test creating Zendesk tickets in the apps.

According to Zendesk, a workaround for this is to programmatically append "+testing" when a ticket is submitted from an @automattic.com or @a8c.com email address. This PR does just that.

To test:

• Sign into an account with an Automattic email, or modify this line to use a hard-coded Automattic email
• Verify that the feedback form now works
• Verify that you can now submit support tickets

[dangermattic]

	2 Warnings
:warning:	strings.xml files should only be updated on release branches, when the translations are downloaded by our automation.
:warning:	PR is not assigned to a milestone.

Generated by :no_entry_sign: Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21453-7d77222
	Commit	7d7722286e3edf1e4568fef280ef1a99008aa701
	Direct Download	wordpress-prototype-build-pr21453-7d77222.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21453-7d77222
	Commit	7d7722286e3edf1e4568fef280ef1a99008aa701
	Direct Download	jetpack-prototype-build-pr21453-7d77222.apk

Note: Google Login is not supported on these builds.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 39.50%. Comparing base (535baed) to head (7d77222). Report is 70 commits behind head on trunk.

Files with missing lines	Patch %	Lines
.../java/org/wordpress/android/ui/prefs/AppPrefs.java	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## trunk #21453 +/- ## ======================================= Coverage 39.50% 39.50% ======================================= Files 2119 2119 Lines 99437 99437 Branches 15282 15282 ======================================= Hits 39281 39281 Misses 56674 56674 Partials 3482 3482 ```

:umbrella: View full report in Codecov by Sentry.
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[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud