Fixed maven central 501 error, using of https.

[roldevg]

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Description

Motivation and Context

Hi, guys!

I started to learn the documentation, but get an error on the screenshot.
So, we need to change the documentation for the actual link.

Effective January 15, 2020, The Central Repository no longer supports insecure communication over plain HTTP and requires that all requests to the repository are encrypted over HTTPS.

If you're receiving this error, then you need to replace all URL references to Maven Central with their canonical HTTPS counterparts:

Replace http://repo1.maven.org/maven2/ with https://repo1.maven.org/maven2/

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)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[claassistantio]

All committers have signed the CLA.

[roldevg]

It seems the Travis CI has some problems with javadocs generation: https://travis-ci.com/SeleniumHQ/selenium/jobs/280443357

[shs96c]

Thank you for catching this, and welcome to the project!