remove period_helper from non-period reqs (pandas-dev#17531)

Author: jbrockmendel

setup.py

@@ -461,7 +461,6 @@ def pxd(name):
 
 tseries_depends = ['pandas/_libs/src/datetime/np_datetime.h',
  'pandas/_libs/src/datetime/np_datetime_strings.h',
- 'pandas/_libs/src/period_helper.h',
  'pandas/_libs/src/datetime.pxd']
 
 
@@ -478,11 +477,11 @@ def pxd(name):
  'pxdfiles': ['_libs/src/util'],
  'depends': tseries_depends,
  'sources': ['pandas/_libs/src/datetime/np_datetime.c',
- 'pandas/_libs/src/datetime/np_datetime_strings.c',
- 'pandas/_libs/src/period_helper.c']},
+ 'pandas/_libs/src/datetime/np_datetime_strings.c']},
  '_libs.tslibs.timezones': {'pyxfile': '_libs/tslibs/timezones'},
  '_libs.period': {'pyxfile': '_libs/period',
- 'depends': tseries_depends,
+ 'depends': (tseries_depends +
+ ['pandas/_libs/src/period_helper.h']),
  'sources': ['pandas/_libs/src/datetime/np_datetime.c',
  'pandas/_libs/src/datetime/np_datetime_strings.c',
  'pandas/_libs/src/period_helper.c']},