pin serde on MSRV

Author: Marcondiro

.github/workflows/ci.yml

@@ -62,6 +62,9 @@ jobs:
         uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ needs.get-package-info.outputs.msrv }}
+      - name: Use compatible serde
+        if: matrix.rust == needs.get-package-info.outputs.msrv
+        run: cargo update -p serde --precise 1.0.152 --verbose
       - name: Build
         run: cargo build --verbose
       - name: Run tests with all features