Add support for read-only caching in v2

src/post.ts

@@ -1,16 +1,8 @@
-import * as core from '@actions/core'
-
 import * as caches from './caches'
 
 // Invoked by GitHub Actions
 export async function run(): Promise<void> {
-    if (isCacheReadOnly()) return
-
     await caches.save()
 }
 
-function isCacheReadOnly(): boolean {
-    return core.getBooleanInput('cache-read-only')
-}
-
 run()