Remove redundant install_executorch.sh call in QNN CI job

Summary:

setup-linux.sh is calling install_executorch.sh already so let's remove
the redundant call.

Test Plan:

Reviewers:

Subscribers:

Tasks:

Tags:

Author: larryliu0820

.github/workflows/pull.yml

@@ -573,7 +573,6 @@ jobs:
 
         BUILD_TOOL="cmake"
 
-        ./install_requirements.sh --use-pt-pinned-commit
         PYTHON_EXECUTABLE=python bash .ci/scripts/setup-qnn-deps.sh
         PYTHON_EXECUTABLE=python bash .ci/scripts/build-qnn-sdk.sh