Fix template link in documentation

[sanzoghenzo]

Description of your changes

The first link needed for a beginner to start with the provider generation was broken. It now points to the updated repository location.

I have:

• Read and followed Upjet's contribution process.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

[sergenyalcin]

@sanzoghenzo thanks for this fix. There is a problem about signing-off the commit. The DCO check failed. It seems you successfully signed-off the commit but also the signing-off message must be in the commit message like:

Signed-off-by: Name Mail

[Upbound-CLA]

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[jeanduplessis]

Since the template repo is now in the crossplane org this PR is no longer needed.