Remove actions/github, update actions/core (#299)

*Issue #, if available:*

*Description of changes:* 
- Removed unused dependency `@actions/github` to remove dependency on
`undici 5.x` and address CVE.
- Moved to `@actions/core 2.0.0`. Moving to `@actions/core 3.0.0` seems
more extensive, will leave that for a later CR.


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Author: simonmarty

dist/136.index.js

@@ -728,7 +728,7 @@ const core_1 = __webpack_require__(8704);
 const util_user_agent_node_1 = __webpack_require__(1656);
 const config_resolver_1 = __webpack_require__(9316);
 const core_2 = __webpack_require__(402);
-const hash_node_1 = __webpack_require__(5092);
+const hash_node_1 = __webpack_require__(2711);
 const middleware_retry_1 = __webpack_require__(9618);
 const node_config_provider_1 = __webpack_require__(5704);
 const node_http_handler_1 = __webpack_require__(1279);