Use 1.68 for MSRV check (sparse protocol)

Signed-off-by: Nico Burns <[email protected]>

Author: nicoburns

.github/workflows/main.yml

@@ -37,7 +37,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: 1.66
+          toolchain: 1.68
       - run: cargo check --lib --all-features
 
   format: