Bump MSRV to match objc2's MSRV

Author: madsmtm

.github/workflows/rust.yml

@@ -34,7 +34,7 @@ jobs:
     - name: Install toolchain
       uses: actions-rs/toolchain@v1
       with:
-        toolchain: 1.56.1
+        toolchain: '1.60'
         override: true
     - name: Build
       run: cargo build --verbose