Bump @actions/core to 1.9.1 (#56)

Fixes CVE-2022-35954. Does not look like anything terriblity important
to me, but hey, audit is happy.

node_modules/@actions/core/lib/oidc-utils.d.ts

@@ -0,0 +1,7 @@
+export declare class OidcClient {
+    private static createHttpClient;
+    private static getRequestToken;
+    private static getIDTokenUrl;
+    private static getCall;
+    static getIDToken(audience?: string): Promise<string>;
+}