Fix variable assignment syntax for Python version in apigee-build.yml

Author: sathiya-nhs

azure/common/apigee-build.yml

@@ -147,7 +147,7 @@ jobs:
           service_name: "${{ parameters.service_name }}"
 
       - bash: |
-          pyversion="$python_version"
+          pyversion="$(python_version)"
           PATCH=$(curl -fsSL https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json \
           | jq -r --arg pyversion "$pyversion" '[ .[] | select(.stable == true) | .version
           | select(test("^" + ($pyversion|gsub("\\.";"\\.")) + "\\.\\d+$")) | split(".") | map(tonumber)] | max | join(".")')