Updated README for out-of-band release. (Azure#21038)

Author: vcolin7

sdk/keyvault/azure-security-keyvault-keys/README.md

@@ -14,7 +14,7 @@ Maven dependency for the Azure Key Vault Key client library. Add it to your proj
 <dependency>
     <groupId>com.azure</groupId>
     <artifactId>azure-security-keyvault-keys</artifactId>
-    <version>4.2.7</version>
+    <version>4.3.0-beta.7</version>
 </dependency>
 ```
 [//]: # ({x-version-update-end})