Bump syn from 1.0.80 to 1.0.81 (#4155)

Bumps [syn](https://github.com/dtolnay/syn) from 1.0.80 to 1.0.81.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](https://github.com/dtolnay/syn/compare/1.0.80...1.0.81)

---
updated-dependencies:
- dependency-name: syn
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

polkadot/Cargo.lock

@@ -7378,9 +7378,9 @@ checksum = "eba180dafb9038b050a4c280019bbedf9f2467b61e5d892dcad585bb57aadc5a"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.30"
+version = "1.0.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "edc3358ebc67bc8b7fa0c007f945b0b18226f78437d61bec735a9eb96b61ee70"
+checksum = "ba508cc11742c0dc5c1659771673afbab7a0efab23aa17e854cbab0837ed0b43"
 dependencies = [
  "unicode-xid",
 ]
@@ -10393,9 +10393,9 @@ checksum = "6bdef32e8150c2a081110b42772ffe7d7c9032b606bc226c8260fd97e0976601"
 
 [[package]]
 name = "syn"
-version = "1.0.80"
+version = "1.0.81"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d010a1623fbd906d51d650a9916aaefc05ffa0e4053ff7fe601167f3e715d194"
+checksum = "f2afee18b8beb5a596ecb4a2dce128c719b4ba399d34126b9e4396e3f9860966"
 dependencies = [
  "proc-macro2",
  "quote",