Update Maven Central badge in Geb README.md #7115

Job	Run time
Hibernate5 Functional Tests (25)	13m 45s
Mongodb Functional Tests (25, 7.0)	17m 29s
Build Grails-Core Rerunning all Tasks (ubuntu-latest, 17)	32m 54s
Build Gradle Plugins (17)	1m 15s
Build Grails-Core (ubuntu-latest, 25)	26m 50s
Mongodb Functional Tests (25, 8.0)	17m 22s
Mongodb Functional Tests (17, 7.0)	18m 39s
Build Grails Forge (21)	15m 35s
Hibernate5 Functional Tests (17)	15m 23s
Build Grails Forge (17)	19m 29s
Mongodb Functional Tests (17, 8.0)	19m 17s
Build Grails-Core (windows-latest, 25)	41m 24s
Functional Tests (17)	26m 18s
Functional Tests (21)	23m 1s
Build Grails-Core (ubuntu-latest, 21)	28m 56s
Build Grails-Core (macos-latest, 21)	59m 18s
Build Grails-Core (ubuntu-latest, 17)	31m 54s
Functional Tests (25)	23m 38s
Build Gradle Plugins (25)	1m 11s
publishGradle	0s
publishForge	0s
publish	0s
docs	0s
	7h 13m 38s

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