tests/eepreg: remove duplicate FEATURES_REQUIRED

The dependency from eepreg to FEATURES_REQUIRED is already defined in
`sys/Makefile.dep` so should not need to be duplicated in the
application Makefile.

tests/eepreg/Makefile

 include ../Makefile.tests_common
 
-FEATURES_REQUIRED = periph_eeprom
-
 USEMODULE += eepreg
 
 include $(RIOTBASE)/Makefile.include