samples: userspace: exclude cy8cproto boards from sample

Excluded cy8cproto_062_4343w and cy8cproto_063_ble from
samples/userspace/shared_mem sample due to a hardware
limitation with number of available MPU regions.
Sample throws warning:
`num_parts of 4 exceeds maximum allowable partitions (2)`
With the Cortex M4 on the boards only 2 mpu regions are left
and available to be used with the sample.

Signed-off-by: Pavlo Havrylyuk <pavlo.havrylyuk@infineon.com>