update changelog for release 4.6.15 #1885

Job	Run time
supported_jdks (core, 17)	2m 6s
latest_jdk (ubuntu-latest, core)	1m 51s
supported_jdks (core, 18)	2m 3s
latest_jdk (ubuntu-latest, consumer -x :consumer:junit:clojureTest)	3m 7s
supported_jdks (consumer, 17)	3m 35s
latest_jdk (ubuntu-latest, provider)	3m 32s
supported_jdks (consumer, 18)	3m 19s
latest_jdk (ubuntu-latest, pact-specification-test)	1m 31s
supported_jdks (provider, 17)	4m 13s
latest_jdk (windows-latest, core)	2m 56s
supported_jdks (provider, 18)	3m 28s
latest_jdk (windows-latest, consumer -x :consumer:junit:clojureTest)	4m 9s
supported_jdks (pact-specification-test, 17)	1m 49s
latest_jdk (windows-latest, provider)	5m 11s
supported_jdks (pact-specification-test, 18)	1m 27s
latest_jdk (windows-latest, pact-specification-test)	2m 19s
latest_jdk (macos-latest, core)	1m 32s
latest_jdk (macos-latest, consumer -x :consumer:junit:clojureTest)	4m 48s
latest_jdk (macos-latest, provider)	3m 39s
latest_jdk (macos-latest, pact-specification-test)	1m 10s
	57m 45s

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