[Docs] Update deprecation date

[pedrosousa]

The deprecation date of the following resources has been updated:

• cloudflare_filter
• cloudflare_firewall_rule
• cloudflare_rate_limit

The Developer Docs have the correct date already (2025-06-15):

• https://developers.cloudflare.com/waf/reference/migration-guides/firewall-rules-to-custom-rules/
• https://developers.cloudflare.com/waf/reference/migration-guides/old-rate-limiting-deprecation/

[github-actions]

Oops! It looks like no changelog entry is attached to this PR. Please include a release note as described in https://github.com/cloudflare/terraform-provider-cloudflare/blob/master/contributing/changelog-process.md.

Example:

```release-note:TYPE
Release note
```

If you do not require a release note to be included and you have permission, please add the workflow/skip-changelog-entry label. Otherwise, a maintainer will add the label or ask you for one when they review the PR.

[github-actions]

This functionality has been released in v4.49.0 of the Terraform Cloudflare Provider.

Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!