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']},