ci: select winapi-util 0.1.5 in pinned build

winapi-util has bumped its MSRV, but termcolor still works fine with
winapi-util <0.1.6.

(I didn't bother figuring out winapi-util's actual MSRV, but it does at
least build with Rust 1.60. So it's unlikely to be a problem in
practice.)

.github/workflows/ci.yml

@@ -12,15 +12,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        build:
-        - pinned
-        - pinned-win
-        - stable
-        - beta
-        - nightly
-        - macos
-        - win-msvc
-        - win-gnu
         include:
         - build: pinned
           os: ubuntu-latest
@@ -53,6 +44,10 @@ jobs:
       uses: dtolnay/rust-toolchain@master
       with:
         toolchain: ${{ matrix.rust }}
+    # Newer versions of winapi-util require newer Rust. So just build with an
+    # older version for now.
+    - if: matrix.build == 'pinned' || matrix.build == 'pinned-win'
+      run: cargo update -p winapi-util --precise 0.1.5
     - run: cargo build --verbose
     - run: cargo doc --verbose
     - run: cargo test --verbose