Bump rxjs from 6.6.2 to 7.8.1 in /core

Bumps [rxjs](https://github.com/reactivex/rxjs) from 6.6.2 to 7.8.1.
- [Release notes](https://github.com/reactivex/rxjs/releases)
- [Changelog](https://github.com/ReactiveX/rxjs/blob/7.8.1/CHANGELOG.md)
- [Commits](ReactiveX/rxjs@6.6.2...7.8.1)

---
updated-dependencies:
- dependency-name: rxjs
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

core/package.json

@@ -16,7 +16,7 @@
     "lodash": "^4.17.21",
     "moment": "^2.29.1",
     "path-exists": "^5.0.0",
-    "rxjs": "^6.6.2",
+    "rxjs": "^7.8.1",
     "rxjs-compat": "^6.6.7",
     "stream": "0.0.2",
     "typescript": "^5.0.4"