Add JMX metrics gatherer version 1.39.0-alpha (open-telemetry#35268)

Add JMX metrics gatherer version `1.39.0-alpha`.

cc @open-telemetry/java-contrib-approvers

Author: opentelemetrybot

receiver/jmxreceiver/supported_jars.go

@@ -31,6 +31,10 @@ func oldFormatProperties(c *Config, j supportedJar) error {
 // If you change this variable name, please open an issue in opentelemetry-java-contrib
 // so that repository's release automation can be updated
 var jmxMetricsGathererVersions = map[string]supportedJar{
+	"43543679b12c7772fffe78ad9dcde3421cb5dd2a704231f9901d32578b2cf69e": {
+		version: "1.39.0-alpha",
+		jar:     "JMX metrics gatherer",
+	},
 	"75d03922df2306086b9eee2daccbfd8c9b94ce140a482fb4698a839ec3d3f192": {
 		version: "1.38.0-alpha",
 		jar:     "JMX metrics gatherer",