Update dataflow.py (#19231)

airflow/providers/google/cloud/hooks/dataflow.py

@@ -899,7 +899,7 @@ def build_dataflow_job_name(job_name: str, append_job_name: bool = True) -> str:
 
         if not re.match(r"^[a-z]([-a-z0-9]*[a-z0-9])?$", base_job_name):
             raise ValueError(
-                f"Invalid job_name ({base_job_name}); the name must consist ofonly the characters "
+                f"Invalid job_name ({base_job_name}); the name must consist of only the characters "
                 f"[-a-z0-9], starting with a letter and ending with a letter or number "
             )