chore(core): remove unused rxjs peer dependency

The runtime rxjs import (bufferChainSyncEvent) that made rxjs required
was hoisted out of core, and core no longer references rxjs anywhere in
its source or emitted types. The leftover peerDependencies/
peerDependenciesMeta entries are now dead. Resolves the residue of #1001.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: rhyslbw

packages/core/package.json

@@ -47,14 +47,6 @@
     "tsc-alias": "^1.8.10",
     "typescript": "^4.7.4"
   },
-  "peerDependencies": {
-    "rxjs": "^7.4.0"
-  },
-  "peerDependenciesMeta": {
-    "rxjs": {
-      "optional": true
-    }
-  },
   "dependencies": {
     "@biglup/is-cid": "^1.0.3",
     "@cardano-ogmios/client": "6.9.0",