add pythonpath to the coverage run

Author: rpcme

.github/workflows/coverage.yml

@@ -16,7 +16,7 @@ jobs:
             - name: 'Run coverage'
               run: |
                   export AWS_DEFAULT_REGION=us-east-1
-                  PYTHONPATH=$(pwd)/src/layer_utils
+                  export PYTHONPATH=$(pwd)/src/layer_utils
                   coverage run --source=src/bulk_importer,src/product_provider,src/provider_espressif,src/provider_infineon,src/provider_microchip -m pytest
                   coverage report -m
             - name: Coverage Badge