Re-pin idna_adapter to for MSRV builds

.. we previously dropped the pin when moving MSRV to 1.85, but it seems
that is not sufficient anymore..

Author: tnull

.github/workflows/rust.yml

@@ -41,6 +41,10 @@ jobs:
       - name: Check formatting on Rust ${{ matrix.toolchain }}
         if: matrix.check-fmt
         run: rustup component add rustfmt && cargo fmt --all -- --check
+      - name: Pin packages to allow for MSRV
+        if: matrix.msrv
+        run: |
+          cargo update -p idna_adapter --precise "1.2.0" --verbose # idna_adapter 1.2.1 uses ICU4X 2.2.0, requiring 1.86 and newer
       - name: Set RUSTFLAGS to deny warnings
         if: "matrix.toolchain == 'stable'"
         run: echo "RUSTFLAGS=-D warnings" >> "$GITHUB_ENV"