fix(services/s3): Remove not needed check for batch delete

[Xuanwo]

Which issue does this PR close?

None

Rationale for this change

One of opendal users report a panic in opendal:

2025-05-16T06:55:27.909244+00:00[Etc/UTC]  WARN storage::service: service.rs:103 opendal will retry after 2.563914299s because: RateLimited (temporary) at delete => S3Error { code: "SlowDown", message: "Please reduce your request rate.", resource: "", request_id: "x" }

Context:
   uri: http://xxx.s3.cn-northwest-1.amazonaws.com.cn/?delete
   response: Parts { status: 503, version: HTTP/1.1, headers: {"x-amz-request-id": "x", "x-amz-id-2": "x", "content-type": "application/xml", "transfer-encoding": "chunked", "date": "Fri, 16 May 2025 06:55:27 GMT", "connection": "close", "server": "AmazonS3"} }
   service: s3
   deleted: 0
 node_id=x nodegroup=x
2025-05-16T06:55:27.921869+00:00[Etc/UTC] ERROR runtime::global: global.rs:105 panic occurred: panicked at /usr/local/cargo/registry/src/index.crates.io-1949cf8c6b5b557f/opendal-0.53.1/src/services/s3/delete.rs:73:36:
removal index (is 0) should be < len (is 0)
backtrace:
   0: std::backtrace_rs::backtrace::libunwind::trace
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1: std::backtrace_rs::backtrace::trace_unsynchronized
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
   2: std::backtrace::Backtrace::create
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/std/src/backtrace.rs:331:13
   3: runtime::global::set_panic_hook::{{closure}}
             at /build/crates/runtime/src/global.rs:104:25
   4: <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/alloc/src/boxed.rs:1980:9
   5: std::panicking::rust_panic_with_hook
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/std/src/panicking.rs:841:13
   6: std::panicking::begin_panic_handler::{{closure}}
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/std/src/panicking.rs:706:13
   7: std::sys::backtrace::__rust_end_short_backtrace
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/std/src/sys/backtrace.rs:168:18
   8: __rustc::rust_begin_unwind
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/std/src/panicking.rs:697:5
   9: core::panicking::panic_fmt
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/core/src/panicking.rs:75:14
  10: core::fmt::Arguments::new_v1
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/core/src/fmt/mod.rs:643:9
  11: alloc::vec::Vec<T,A>::remove::assert_failed
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/alloc/src/vec/mod.rs:2071:13
  12: alloc::vec::Vec<T,A>::remove
             at /rustc/6bc57c6bf7d0024ad9ea5a2c112f3fc9c383c8a4/library/alloc/src/vec/mod.rs:2076:13
  13: <opendal::services::s3::delete::S3Deleter as opendal::raw::oio::delete::batch_delete::BatchDelete>::delete_batch::{{closure}}
             at /usr/local/cargo/registry/src/index.crates.io-1949cf8c6b5b557f/opendal-0.53.1/src/services/s3/delete.rs:73:23

It appears that AWS S3 can return an Ok response even if no files were actually removed successfully. The best thing here we can do is just remove this check.

What changes are included in this PR?

Remove the early check to return error.

Are there any user-facing changes?

No.