Pin flytekit to 1.15.0 to unblock functional tests (#6330)

Signed-off-by: Eduardo Apolinario <[email protected]>
Co-authored-by: Eduardo Apolinario <[email protected]>

Author: eapolinario

.github/workflows/single-binary.yml

@@ -176,7 +176,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install uv
-          uv pip install --system flytekit flytekitplugins-deck-standard "numpy<2.0.0" pyarrow pandas
+          uv pip install --system flytekit==1.15.0 flytekitplugins-deck-standard==1.15.0 "numpy<2.0.0" pyarrow pandas
           uv pip freeze
       - name: Checkout flytesnacks
         uses: actions/checkout@v4