Fix typo in the Pull Request "build image" if. (#22585)
Fix typo in the Pull Request "build image" if. (#22585)

In case Pull request is run in the "apache/airflow" repository,
image building happens in the ci.yml workflow as of #22542.

However there was a typo in the build-image workflow that made the
images build in both - BuildImage and CI workflow.
cfei18/incubator-airflow,apache/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,apache/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,nathanielvarona/airflow,cfei18/incubator-airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,apache/airflow,apache/airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,apache/airflow,lyft/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow