Update 10up/simple-local-avatars requirement from ~2.7.7 to ~2.7.8

Updates the requirements on [10up/simple-local-avatars](https://github.com/10up/simple-local-avatars) to permit the latest version.
- [Release notes](https://github.com/10up/simple-local-avatars/releases)
- [Changelog](https://github.com/10up/simple-local-avatars/blob/develop/CHANGELOG.md)
- [Commits](10up/simple-local-avatars@2.7.7...2.7.8)

---
updated-dependencies:
- dependency-name: 10up/simple-local-avatars
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

composer.json

@@ -17,7 +17,7 @@
     "humanmade/clean-html": "^2.0.0",
     "humanmade/altis-reusable-blocks": "~0.2.4",
     "humanmade/asset-loader": "^0.6.4",
-    "10up/simple-local-avatars": "~2.7.7"
+    "10up/simple-local-avatars": "~2.7.8"
   },
   "autoload": {
     "files": [