add better explination why frozen-abi re-exports rand, rand_chacha and bincode

Author: puhtaytow

Cargo.lock

@@ -35,12 +35,14 @@ solana-frozen-abi-macro = { workspace = true }
 thiserror = { workspace = true }
 
 [target.'cfg(not(target_os = "solana"))'.dependencies]
+# This dependency is used only to back `frozen-abi` StableAbi API
+bincode = "1.3.3"
 im = { workspace = true, features = ["rayon", "serde"] }
 memmap2 = { workspace = true }
-# these are re-exports for StableAbi
+# These dependencies are used only to back `frozen-abi` StableAbi API,
+# to avoid version skew and keep digest computation stable regardless of consumer dependencies.
 rand = "0.8.5"
 rand_chacha = "0.3.1"
-bincode = "1.3.3"
 
 [target.'cfg(not(target_os = "solana"))'.dev-dependencies]
 bitflags = { workspace = true, features = ["serde"] }