Raise minimum tested compiler to rust 1.76

Required by the `toml` crate.

Author: dtolnay

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [nightly, beta, stable, 1.81.0, 1.70.0]
+        rust: [nightly, beta, stable, 1.81.0, 1.76.0]
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v5
@@ -40,7 +40,7 @@ jobs:
         if: matrix.rust == 'nightly'
       - run: cargo test --workspace --exclude thiserror_no_std_test
       - run: cargo test --manifest-path tests/no-std/Cargo.toml
-        if: matrix.rust != '1.70.0'
+        if: matrix.rust != '1.76.0'
       - run: cargo test --no-default-features
       - uses: actions/upload-artifact@v4
         if: matrix.rust == 'nightly' && always()