tutorial.md: docker-server value for Docker Hub

[didier-durand]

See comment in #2616

Most people are used to 'docker.io' as server for Docker Hub and not 'index.docker.io'. The tutorial doesn't work with 'docker.io', so defining the value clearly in case of widely-used Docker Hub may be useful.

Best,

Didier

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[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Didier Durand (b7e2505)

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[tekton-robot]

Hi @didier-durand. Thanks for your PR.

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[popcor255]

/ok-to-test

[jerop]

thanks @didier-durand!

/ok-to-test

[jerop]

small nit, we tend to put these caveats after a **Note:** to ensure users don't miss them, as shown in this snippet from another part of this tutorial:

pipeline/docs/tutorial.md

Line 14 in b7e2505

**Note:** Items requiring configuration are marked with the `#configure` annotation.

[jerop]

/kind documentation

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[didier-durand]

@jerop : no interest in merging this typo fix? Didier

[chmouel]

@didier-durand i believe @jerop made a comment here #3298 (comment) and it probably can get merged quickly after that when this is addressed,