Pin syn too.

Author: sunfishcode

.github/workflows/main.yml

@@ -64,6 +64,7 @@ jobs:
         cargo update --package=rayon-core --precise=1.12.1
         cargo update --package=windows-sys@0.61.2 --precise=0.60.2
         cargo update --package=quote --precise=1.0.41
+        cargo update --package=syn --precise=2.0.106
 
     - run: >
         rustup target add
@@ -548,6 +549,7 @@ jobs:
         cargo update --package=rayon-core --precise=1.12.1
         cargo update --package=windows-sys@0.61.2 --precise=0.60.2
         cargo update --package=quote --precise=1.0.41
+        cargo update --package=syn --precise=2.0.106
 
     - run: |
         cargo test --verbose --features=all-apis --release --workspace -- --nocapture