fix syntax for release platform check in syft-install-check workflow

Author: shubham3121

.github/workflows/cd-post-release-tests.yml

@@ -162,10 +162,10 @@ jobs:
 
       - name: Install Syft
         run: |
-          if [[ "${{ inputs.release_platform }}" == "REAL_PYPI" ]]; then
+          if (${{ inputs.release_platform }} == "REAL_PYPI"); then
             pip install syft==${{ inputs.syft_version }}
           fi
-          if [[ "${{ inputs.release_platform }}" == "TEST_PYPI" ]]; then
+          if (${{ inputs.release_platform }}" == "TEST_PYPI"); then
             pip install -i https://test.pypi.org/simple/ syft==${{ inputs.syft_version }}
           fi