Fix CI Rust cache working directory (#50)

Author: cretz

.github/workflows/ci.yml

@@ -30,6 +30,8 @@ jobs:
         with:
           toolchain: stable
       - uses: Swatinem/rust-cache@v1
+        with:
+          working-directory: temporalio/bridge
       - uses: actions/setup-python@v1
         with:
           python-version: ${{ matrix.python }}
@@ -93,6 +95,8 @@ jobs:
         with:
           toolchain: stable
       - uses: Swatinem/rust-cache@v1
+        with:
+          working-directory: temporalio/bridge
       - uses: actions/setup-python@v1
         with:
           python-version: "3.10"