fix: getAuthenticatedOctokit is a standalone method (#5235)

fixes
```
TypeError: Cannot read properties of undefined (reading 'getAuthenticatedOctokit')
    at eachInstallation (/usr/src/app/node_modules/gcf-utils/build/src/installations.js:26:32)
    at eachInstallation.next (<anonymous>)
    at GCFBootstrapper.handleScheduledInstallation (/usr/src/app/node_modules/gcf-utils/build/src/gcf-utils.js:492:30)
    at GCFBootstrapper.handleScheduled (/usr/src/app/node_modules/gcf-utils/build/src/gcf-utils.js:447:24)
    at /usr/src/app/node_modules/gcf-utils/build/src/gcf-utils.js:290:32
```

packages/gcf-utils/src/installations.ts

@@ -14,6 +14,7 @@
 //
 
 import {WrapConfig} from './configuration';
+import {getAuthenticatedOctokit} from './gcf-utils';
 
 // Helper interface to abstract the response of the list installations GitHub response
 export interface AppInstallation {
@@ -49,9 +50,9 @@ export interface InstalledRepository {
 export async function* eachInstallation(
   wrapConfig: WrapConfig
 ): AsyncGenerator<AppInstallation, void, void> {
-  const octokit = await this.getAuthenticatedOctokit(undefined, wrapConfig);
+  const octokit = await getAuthenticatedOctokit(undefined);
   const installationsPaginated = octokit.paginate.iterator(
-    octokit.apps.listInstallations
+    octokit.apps.listInstallations as any
   );
   for await (const response of installationsPaginated) {
     for (const installation of response.data) {
@@ -75,12 +76,9 @@ export async function* eachInstalledRepository(
   installationId: number,
   wrapConfig: WrapConfig
 ): AsyncGenerator<InstalledRepository, void, void> {
-  const octokit = await this.getAuthenticatedOctokit(
-    installationId,
-    wrapConfig
-  );
+  const octokit = await getAuthenticatedOctokit(installationId);
   const installationRepositoriesPaginated = octokit.paginate.iterator(
-    octokit.apps.listReposAccessibleToInstallation,
+    octokit.apps.listReposAccessibleToInstallation as any,
     {
       mediaType: {
         previews: ['machine-man'],