Revert "[nrf noup] zephyr: Restore default RTC user channel count"

This reverts commit abaff57.

Signed-off-by: Jamie McCrae <[email protected]>

Author: nordicjm

boot/zephyr/prj.conf

@@ -34,4 +34,3 @@ CONFIG_MCUBOOT_LOG_LEVEL_INF=y
 CONFIG_CBPRINTF_NANO=y
 ### Use the minimal C library to reduce flash usage
 CONFIG_MINIMAL_LIBC=y
-CONFIG_NRF_RTC_TIMER_USER_CHAN_COUNT=0