bump gax version to 1.4.2 (#2242)
bump gax version to 1.4.2 (#2242)


vam-google/google-cloud-java,shinfan/gcloud-java,shinfan/gcloud-java,vam-google/google-cloud-java,FirebasePrivate/google-cloud-java,shinfan/gcloud-java,FirebasePrivate/google-cloud-java,vam-google/google-cloud-java,vam-google/google-cloud-java,mbrukman/gcloud-java,vam-google/google-cloud-java,FirebasePrivate/google-cloud-java,mbrukman/gcloud-java,shinfan/gcloud-java,mbrukman/gcloud-java,FirebasePrivate/google-cloud-java,shinfan/gcloud-java,mbrukman/gcloud-java,vam-google/google-cloud-java,FirebasePrivate/google-cloud-java