refactor: update bundler cache key generation

Simplify the generation of the bundler cache key by including the repository name in the key. This ensures that the cache is specific to the repository being worked on. The previous key generation included the complete working directory path, but the working directory of hosted and self-hosted runners are different, so cache hits miss on self-hosted or vice-versa.

bundler.js

@@ -234,10 +234,11 @@ export async function bundleInstall(gemfile, lockFile, platform, engine, rubyVer
 
 async function computeBaseKey(platform, engine, version, lockFile, cacheVersion) {
   const cwd = process.cwd()
+  const repoName = path.basename(cwd)
   const bundleWith = process.env['BUNDLE_WITH'] || ''
   const bundleWithout = process.env['BUNDLE_WITHOUT'] || ''
   const bundleOnly = process.env['BUNDLE_ONLY'] || ''
-  let key = `setup-ruby-bundler-cache-v6-${common.getOSNameVersionArch()}-${engine}-${version}-wd-${cwd}-with-${bundleWith}-without-${bundleWithout}-only-${bundleOnly}`
+  let key = `setup-ruby-bundler-cache-v6-${common.getOSNameVersionArch()}-${engine}-${version}-repo-${repoName}-with-${bundleWith}-without-${bundleWithout}-only-${bundleOnly}`
 
   if (cacheVersion !== DEFAULT_CACHE_VERSION) {
     key += `-v-${cacheVersion}`