Update link to pip's caching guide in examples.md

[Magnus167]

Description

As highlighted under Finding Packages section of PyPA pip documentation website, the pip's caching documentation has moved to this page here: https://pip.pypa.io/en/stable/topics/caching/ .

Motivation and Context

The link was out of date, needed to be updated.

How Has This Been Tested?

Non-code changes. The domain for the URL remains the same so no security issues.
As a test, I simply viewed the MD file on repository - repo:Magnus167/cache branch:Magnus167docs-pypi-link-update file:examples.md , and checked if the link in the file worked correctly.

Screenshots (if appropriate):

(screenshot from https://pip.pypa.io/en/stable/cli/pip_install/)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (add or update README or docs)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.