gradle.properties needs to be the source of truth for Maven builds

[cer]

It's too error prone otherwise.

eventuate-tram-examples-customers-and-orders/build-and-test-all-mysql-maven.sh

Line 5 in 4d5206b

export EVENTUATE_COMMON_VERSION=0.8.0.RELEASE

And

eventuate-tram-examples-customers-and-orders/pom.xml

Lines 16 to 18 in 4d5206b

	<eventuateTramVersion>0.22.0.RC8</eventuateTramVersion>
	<springBootVersion>2.1.5.RELEASE</springBootVersion>
	<eventuateUtilVersion>0.2.0.RELEASE</eventuateUtilVersion>