doc: release: 2.7: add list of closed issues
doc: release: 2.7: add list of closed issues

This change adds the list of closed issue as per the release
process.

Signed-off-by: Christopher Friedt <76f728c1c3997bf5bfe7e9261eff720c92409a2f@gmail.com>

finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr