Fix for #357 - error on moodle upgrade mysql 8 #552

Job	Run time
ci / check if job needs to run	4s
ci / prepare test matrix	20s
ci / MOODLE_35_STABLE - mariadb - php 7.1 - tool_excimer	3m 10s
ci / MOODLE_311_STABLE - mariadb - php 7.3 - tool_excimer	2m 55s
ci / MOODLE_35_STABLE - pgsql - php 7.1 - tool_excimer	2m 52s
ci / MOODLE_35_STABLE - mariadb - php 7.2 - tool_excimer	3m 23s
ci / MOODLE_35_STABLE - pgsql - php 7.2 - tool_excimer	2m 51s
ci / MOODLE_36_STABLE - mariadb - php 7.1 - tool_excimer	2m 56s
ci / MOODLE_37_STABLE - pgsql - php 7.2 - tool_excimer	4m 16s
ci / MOODLE_39_STABLE - mariadb - php 7.2 - tool_excimer	3m 33s
ci / MOODLE_310_STABLE - pgsql - php 7.2 - tool_excimer	3m 35s
ci / MOODLE_39_STABLE - pgsql - php 7.2 - tool_excimer	3m 50s
ci / MOODLE_39_STABLE - mariadb - php 7.3 - tool_excimer	3m 16s
ci / MOODLE_400_STABLE - pgsql - php 7.3 - tool_excimer	3m 18s
ci / MOODLE_38_STABLE - mariadb - php 7.3 - tool_excimer	3m 41s
ci / MOODLE_401_STABLE - pgsql - php 7.4 - tool_excimer	3m 31s
ci / MOODLE_401_STABLE - mariadb - php 7.4 - tool_excimer	3m 13s
ci / MOODLE_39_STABLE - pgsql - php 7.3 - tool_excimer	3m 16s
ci / MOODLE_401_STABLE - pgsql - php 8.0 - tool_excimer	3m 34s
ci / MOODLE_401_STABLE - mariadb - php 8.0 - tool_excimer	3m 45s
ci / Release to the Moodle plugin directory	0s
	1h 1m 19s

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