TYP: update setup.cfg (#36854)

Author: simonjayhawkins

setup.cfg

@@ -208,9 +208,6 @@ check_untyped_defs=False
 [mypy-pandas.core.indexes.multi]
 check_untyped_defs=False
 
-[mypy-pandas.core.indexes.period]
-check_untyped_defs=False
-
 [mypy-pandas.core.indexes.range]
 check_untyped_defs=False
 
@@ -244,9 +241,6 @@ check_untyped_defs=False
 [mypy-pandas.core.series]
 check_untyped_defs=False
 
-[mypy-pandas.core.strings]
-check_untyped_defs=False
-
 [mypy-pandas.core.window.common]
 check_untyped_defs=False