chore: remove unused import in function.py (#1502)

Author: jialuoo

bigframes/functions/function.py

@@ -35,7 +35,6 @@
 import bigframes.dtypes
 import bigframes.exceptions as bfe
 import bigframes.formatting_helpers as bf_formatting
-import bigframes.functions.function_template
 
 from . import _function_session as bff_session
 from . import _utils