build(deps): bump syn from 1.0.67 to 1.0.68

Bumps [syn](https://github.com/dtolnay/syn) from 1.0.67 to 1.0.68.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](https://github.com/dtolnay/syn/compare/1.0.67...1.0.68)

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

Cargo.lock

@@ -1288,9 +1288,9 @@ checksum = "bc881b2c22681370c6a780e47af9840ef841837bc98118431d4e1868bd0c1086"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.24"
+version = "1.0.26"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e0704ee1a7e00d7bb417d0770ea303c1bccbabf0ef1667dae92b5967f5f8a71"
+checksum = "a152013215dca273577e18d2bf00fa862b89b24169fb78c4c95aeb07992c9cec"
 dependencies = [
  "unicode-xid",
 ]
@@ -1707,9 +1707,9 @@ checksum = "1e81da0851ada1f3e9d4312c704aa4f8806f0f9d69faaf8df2f3464b4a9437c2"
 
 [[package]]
 name = "syn"
-version = "1.0.67"
+version = "1.0.68"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6498a9efc342871f91cc2d0d694c674368b4ceb40f62b65a7a08c3792935e702"
+checksum = "3ce15dd3ed8aa2f8eeac4716d6ef5ab58b6b9256db41d7e1a0224c2788e8fd87"
 dependencies = [
  "proc-macro2",
  "quote",