chore(hashes): update serde dependency to workspace

Update serde from 1.0 to 1.0.103 to align with versions used in other
workspace crates. This makes the dependency constraint match reality
since it was almost always implicitly raised by the other crates.

Author: nyonson

hashes/Cargo.toml

@@ -24,7 +24,7 @@ small-hash = []
 [dependencies]
 internals = { package = "bitcoin-internals", path = "../internals" }
 hex = { package = "hex-conservative", version = "0.3.0", default-features = false, optional = true }
-serde = { version = "1.0", default-features = false, optional = true }
+serde = { version = "1.0.103", default-features = false, optional = true }
 
 [dev-dependencies]
 serde_test = "1.0"