Bump fastly/fastly from 8.8.0 to 9.1.0 in /assets

Bumps [fastly/fastly](https://github.com/fastly/terraform-provider-fastly) from 8.8.0 to 9.1.0.
- [Release notes](https://github.com/fastly/terraform-provider-fastly/releases)
- [Changelog](https://github.com/fastly/terraform-provider-fastly/blob/main/CHANGELOG.md)
- [Commits](fastly/terraform-provider-fastly@v8.8.0...v9.1.0)

---
updated-dependencies:
- dependency-name: fastly/fastly
  dependency-version: 9.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

assets/.terraform.lock.hcl

@@ -11,7 +11,7 @@ terraform {
   required_providers {
     fastly = {
       source  = "fastly/fastly"
-      version = "8.8.0"
+      version = "9.1.0"
     }
   }
 }