Fix spelling of PyPI, the Python Package Index

What does this MR do?

The "Packages & Registries" menu item features "PyPi" in the "Package Registry" option. (Note the spelling!)

This MR aligns the spelling of "PyPI" with the official spelling of the "Python Package Index", which is an acronym of the initial letters.

See the footer of the PyPI.org website for reference.

What does this MR NOT do?

I left out all the "PyPi" text occurrences in the translation files locale/*/gitlab.po.

I'm happy to follow instructions on how to apply the changes there. I assume this is better generated than updated (but maybe I'm wrong).

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Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

If done properly there should be no risks involved with the change.

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team