[maven-release-plugin] prepare release gitlab4j-api-4.18.0

[maven-release-plugin] prepare release gitlab4j-api-4.17.0

[maven-release-plugin] copy for tag gitlab4j-api-4.16.0

[maven-release-plugin] copy for tag gitlab4j-api-4.15.7

[maven-release-plugin] copy for tag gitlab4j-api-4.15.6

[maven-release-plugin] copy for tag gitlab4j-api-4.15.5

[maven-release-plugin] copy for tag gitlab4j-api-4.15.4

[maven-release-plugin] copy for tag gitlab4j-api-4.15.3

[maven-release-plugin] copy for tag gitlab4j-api-4.15.2

[maven-release-plugin] copy for tag gitlab4j-api-4.15.1