samples: subsys: setting does not apply when sector size is 128K

Exclude the stm32h7 target boards to this samples/subsys/settings
because it does not apply for flash sector flash size larger
than 64K : all those stm32h7 mcu have sector size of 128K
The settings_subsys_init will fails (-33 DOM errno ) when it checks
nvs_sector_size > UINT16_MAX in settings_backend_init()
of the subsys/settings/src/settings_nvs.c

Signed-off-by: Francois Ramu <francois.ramu@st.com>