Fix Gutenberg Mobile dependencies resolution

[fluiddot]

I added a new dependency to the package.json file of Gutenberg Mobile in this PR and I noticed that Metro was throwing an error due to not being able to resolve it.

After checking the extra node modules resolver, I realized that the dependencies that are not resolved via the Gutenberg submodule were considered to be located in the Jetpack submodule, including the ones defined in Gutenberg Mobile. To address this, I basically added a condition that checks if the path exists before considering it a dependency within Jetpack.

Additionally, I removed the dependency email-validator from Gutenberg Mobile because it's already in the Jetpack submodule, in fact, it's not even referenced in the Gutenberg Mobile code.

As a side note, these are the dependencies resolved from the Jetpack submodule:

• @automattic/color-studio
• email-validator

To test:

• CI jobs should be green on this PR
• Demo app should run normally
• As a double-check, verify that the Contact info block works as expected because it's the one that imports the email-validator package.

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]

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[hypest]

LGTM! Let's auto-merge when CI green.

✅ CI jobs should be green on this PR. It was green on 0837df7 already.
✅ Demo app should run normally
✅ As a double-check, verify that the Contact info block works as expected because it's the one that imports the email-validator package. ➡️ I verified that when the email is well-formed, the html output includes a mailto: link, while if not well-formed it's just plain text, just like expected by the code.