Update integration.md to reflect the correct usage of offer url

[Ivansteinium]

Description

Add info to the provider docs about not using name and endpoint when using the url.

Fixes

fixes #449

• Updated docs

[hmlanigan]

@Ivansteinium thank you for the contribution.

This change needs to be made in internal/juju/resource_integation.go in the offer_url endpoint's description inside of the schema. Then run make docs to generate the integration.md file changes.

However I also believe that a code change is necessary to update the schema. The offer_url should contain something like

							Validators: []validator.String{
								stringvalidator.ConflictsWith(path.Expressions{
									path.MatchRoot("name"),
									path.MatchRoot("endpoint"),
								}...),
							},

Please also be aware that bug fix PRs were due 12-April
https://discourse.charmhub.io/t/release-planning-for-the-juju-terraform-provider-v0-12-0/13397

We will attempt to land this by end of week, however the priority is to get the PRs opened by 12-April landed first.

[cderici]

Valid change, lgtm, thanks for the contribution @Ivansteinium!

Before we can land this, though, could you please:

1. run make simplify to run the gofmt, looks like the build workflow is detecting some discrepancy.
2. squash the commits with a descriptive commit message.

Thanks, looking forward to get this in the release coming very soon 👍