Update generating-a-provider.md to fix broken references

[JesseEstum]

Description of your changes

Documentation Updates

Fixes #

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.

How has this code been tested

Not applicable - this is documentation MarkDown only.

[jeanduplessis]

@JesseEstum thanks for trying to fix the guide. The challenge here is that the guide is pointing to https://github.com/crossplane/upjet-provider-template which doesn't yet exist.

https://github.com/upbound/upjet-provider-template is in the process of moving upstream to crossplane org which fixes this.

As soon as this PR, crossplane/upjet-provider-template#59, lands we'll move the repo over. Hopefully, it will be done Mon/Tue next week.

[JesseEstum]

@jeanduplessis Thanks for the feedback. I'm actually quite glad to see your response. After I opened the PR I tried to go through the rest of the steps and couldn't get it to work. This explains why! I'll reference the upstream repo for now and look forward to seeing it move this week (or whenever you get to it).