Don't add fullname tag in 2GP package.xml

[leboff]

Fixes #3415 for the scenario of when building a locked 2GP

[salesforce-cla[bot]]

Thanks for the contribution! It looks like @leboff is an internal user so signing the CLA is not required. However, we need to confirm this.

[pasres]

We are experiencing the same issue and would really appreciate if this could be checked and hopefully merged soon. I commented on @leboff 's other PR here: https://github.com/SFDO-Tooling/CumulusCI/pull/3416#issuecomment-2049817319

[agaudoncr]

We are also experiencing this issue and would really appreciate it if this could be looked into and hopefully merged.

[agaudoncr]

For additional context, we received the following response from Salesforce Support indicating that this is the root of the problem.

CumulusCI creates the package version request it converts from SFDX to MDAPI and puts a package name (<fullName> tag) in the package.xml file. Could you please check the package.xml file of the project (manifest/package.xml) and see if that tag is being added? If so please try removing the tag and create the package.