Bump github.com/nats-io/nats-server/v2 from 2.9.19 to 2.9.21

Bumps [github.com/nats-io/nats-server/v2](https://github.com/nats-io/nats-server) from 2.9.19 to 2.9.21.
- [Release notes](https://github.com/nats-io/nats-server/releases)
- [Changelog](https://github.com/nats-io/nats-server/blob/main/.goreleaser.yml)
- [Commits](https://github.com/nats-io/nats-server/compare/v2.9.19...v2.9.21)

---
updated-dependencies:
- dependency-name: github.com/nats-io/nats-server/v2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/github.com/klauspost/compress/s2/reader.go

@@ -147,6 +147,13 @@ type Reader struct {
 	ignoreCRC      bool
 }
 
+// GetBufferCapacity returns the capacity of the internal buffer.
+// This might be useful to know when reusing the same reader in combination
+// with the lazy buffer option.
+func (r *Reader) GetBufferCapacity() int {
+	return cap(r.buf)
+}
+
 // ensureBufferSize will ensure that the buffer can take at least n bytes.
 // If false is returned the buffer exceeds maximum allowed size.
 func (r *Reader) ensureBufferSize(n int) bool {