[Python] Fix mustache tag syntax in github worklow (#20701)

Author: sjoubert

modules/openapi-generator/src/main/resources/python/github-workflow.mustache

@@ -29,4 +29,4 @@ jobs:
           pip install -r test-requirements.txt
       - name: Test with pytest
         run: |
-          pytest --cov={{packageName}}
+          pytest --cov=<%packageName%>

samples/client/echo_api/python-disallowAdditionalPropertiesIfNotPresent/.github/workflows/python.yml

@@ -28,4 +28,4 @@ jobs:
           pip install -r test-requirements.txt
       - name: Test with pytest
         run: |
-          pytest --cov={{packageName}}
+          pytest --cov=openapi_client

samples/client/echo_api/python/.github/workflows/python.yml

@@ -28,4 +28,4 @@ jobs:
           pip install -r test-requirements.txt
       - name: Test with pytest
         run: |
-          pytest --cov={{packageName}}
+          pytest --cov=openapi_client

samples/openapi3/client/petstore/python-aiohttp/.github/workflows/python.yml

@@ -28,4 +28,4 @@ jobs:
           pip install -r test-requirements.txt
       - name: Test with pytest
         run: |
-          pytest --cov={{packageName}}
+          pytest --cov=petstore_api

samples/openapi3/client/petstore/python/.github/workflows/python.yml

@@ -28,4 +28,4 @@ jobs:
           pip install -r test-requirements.txt
       - name: Test with pytest
         run: |
-          pytest --cov={{packageName}}
+          pytest --cov=petstore_api