docs: update Fastly package.json description (#797)

**Requirements**

- [ ] I have added test coverage for new or changed functionality
- [x] I have followed the repository's [pull request submission
guidelines](../blob/main/CONTRIBUTING.md#submitting-pull-requests)
- [ ] I have validated my changes against all supported platform
versions

**Related issues**

https://launchdarkly.atlassian.net/browse/DOCS-973

**Describe the solution you've provided**

package.json `description` field for Fastly is incorrect, this PR
updates it

**Describe alternatives you've considered**

n/a

**Additional context**

I'm not sure what, if anything, needs to happen after this update (is a
patch release required for this to get picked up anywhere?)

Author: mmrj

packages/sdk/fastly/package.json

@@ -2,7 +2,7 @@
   "name": "@launchdarkly/fastly-server-sdk",
   "version": "0.1.0",
   "packageManager": "[email protected]",
-  "description": "Cloudflare LaunchDarkly SDK",
+  "description": "Fastly LaunchDarkly SDK",
   "homepage": "https://github.com/launchdarkly/js-core/tree/main/packages/sdk/fastly",
   "repository": {
     "type": "git",