fix: update comment for arrow-ipc dependency usage in CompressionType and codec features

Author: kosiew

datafusion/physical-plan/Cargo.toml

@@ -49,13 +49,9 @@ name = "datafusion_physical_plan"
 [dependencies]
 arrow = { workspace = true }
 arrow-data = { workspace = true }
-# Feature-only dep used only via the `arrow::ipc` re-export (there is no direct
-# `use arrow_ipc` in this crate): lz4 and zstd codec support required by
-# IPCStreamWriter in spill/mod.rs. These features must stay in sync with the
-# SpillCompression variants in datafusion-common. Declaring the dependency here
-# makes the contract explicit and local to the crate that owns spill, preventing
-# silent regressions if workspace-level arrow-ipc features are narrowed (see
-# #21917 for the documented regression guard around this coupling).
+# Spill IPC writes require lz4 and zstd codec support. Keep these features in
+# sync with the SpillCompression variants in datafusion-common so codec
+# availability is explicit in the crate that owns spill handling.
 arrow-ipc = { workspace = true, features = ["lz4", "zstd"] }
 arrow-ord = { workspace = true }
 arrow-schema = { workspace = true }