west.yml: stm32: Remove PAGESIZE definition

PAGESIZE definition from legacy.h conflicts with POSIX definition.
Since this definition comes from legacy.h file which is only there
for Cube backward compatibility that we don't maintain in Zephyr,
simply remove it.

Note:
This is a second fix for #73363 which wasn't sufficiently tested.
Legacy file is included in stm32yyxx_hal_def.h headers and actually
removing it generates build errors as we're relying on some of the
definitions. Removing this inclusion is necessary and will be done
but on next release.

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>