docs: drop the storage:// crawl protocol from the 15.9 file config API - #508

Summary

Removes the storage:// row from the file crawl path table in the 15.9 file config API reference, across all seven languages.

The MinIO-based storage: client is removed in codelibs/fess-crawler#190 in favor of s3:, which supports S3-compatible object storage through its endpoint parameter.

Change

The separate row is merged into the Amazon S3 row so the S3-compatible case stays documented:

- * - S3-compatible object storage (MinIO, etc.)
-   - ``storage://bucket/path``
- * - Amazon S3
+ * - Amazon S3 / S3-compatible object storage (MinIO, etc.)
    - ``s3://bucket/path``

Applied to de, en, es, fr, ja, ko and zh-cn, each with its own translated label.

Scope

Only the 15.9 tree is touched. Earlier version trees describe releases where storage:// still worked and are left as they are.

This was the only occurrence of storage:// in the 15.9 documentation — the file crawl guide (fileconfig-guide.rst) already listed just file:/, smb://, ftp://, s3:// and gcs://, so no change was needed there.

The admin storage page documentation (storage-guide.rst) is unaffected: that feature uses S3StorageClient and GcsStorageClient on the AWS and Google SDKs, not the MinIO SDK, and continues to work against MinIO servers as an S3-compatible endpoint.