Install icu4c as well

Author: liuzicheng1987

.github/workflows/macos-cxx20-vcpkg.yaml

@@ -54,7 +54,7 @@ jobs:
       - name: Run vcpkg
         uses: lukka/run-vcpkg@v11
       - name: Install ninja 
-        run: brew install ninja autoconf bison flex pkg-config
+        run: brew install ninja autoconf bison flex pkg-config icu4c
         if: matrix.os == 'macos-latest'
       - name: Compile
         if: matrix.db == 'duckdb'