[ci] fix: Fix error in ascend dockerfile (#4265)

### What does this PR do?

Fix error in ascend dockerfile

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Author: FightingZhen

docker/ascend/Dockerfile.ascend_8.3.rc1_a2

@@ -43,7 +43,7 @@ RUN ARCH=$(uname -m) && \
     pip install -e MindSpeed && \
     echo "export PYTHONPATH=\$PYTHONPATH:/Megatron-LM" >> ~/.bashrc && \
     # Remove existing triton or triton-ascend installed by some third-party packages
-    pip uninstall -y triton triton-ascend \
+    pip uninstall -y triton triton-ascend && \
     # Clear extra files
     rm -rf /tmp/* /var/tmp/* && \
     pip cache purge

docker/ascend/Dockerfile.ascend_8.3.rc1_a3

@@ -43,7 +43,7 @@ RUN ARCH=$(uname -m) && \
     pip install -e MindSpeed && \
     echo "export PYTHONPATH=\$PYTHONPATH:/Megatron-LM" >> ~/.bashrc && \
     # Remove existing triton or triton-ascend installed by some third-party packages
-    pip uninstall -y triton triton-ascend \
+    pip uninstall -y triton triton-ascend && \
     # Clear extra files
     rm -rf /tmp/* /var/tmp/* && \
     pip cache purge