Bump chart version to v0.15.0 #1109

Job	Run time
Supported Kubernetes versions End-to-End Tests (8.4.2, 1.29.4)	1h 28m 28s
Supported MySQL versions End-to-End Tests (8.0.28, 1.31.0)	1h 28m 1s
Supported Kubernetes versions End-to-End Tests (8.4.2, 1.30.4)	1h 31m 35s
Integration tests with MySQL (8.0.28)	6m 33s
Supported MySQL versions End-to-End Tests (8.0.36, 1.31.0)	1h 30m 6s
Supported Kubernetes versions End-to-End Tests (8.4.2, 1.31.0)	1h 29m 10s
Integration tests with MySQL (8.0.36)	6m 26s
Supported MySQL versions End-to-End Tests (8.0.37, 1.31.0)	1h 31m 8s
Integration tests with MySQL (8.0.37)	6m 31s
Supported MySQL versions End-to-End Tests (8.0.39, 1.31.0)	1h 29m 14s
Integration tests with MySQL (8.0.39)	6m 32s
Supported MySQL versions End-to-End Tests (8.4.2, 1.31.0)	1h 28m 45s
Upgrade Test	16m 54s
Integration tests with MySQL (8.4.2)	6m 36s
Confirm finishing all tests	1s
	12h 46m 0s

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