[BUG] Wrong configuration properties for Cosmos in Spring Cloud App Configuration App samples

[saragluna]

Describe the bug
This bug was found in this Azure/azure-sdk-for-java#33165. There are two samples in https://github.com/Azure-Samples/azure-spring-boot-samples/blob/main/appconfiguration/azure-spring-cloud-appconfiguration-config/azure-spring-cloud-appconfiguration-config-convert-sample/, the initial one use KV to store the Cosmos key and other properties, and the complete one uses App Configuration + KV to store the configurations.

The bootstrap.properties still uses COSMOS-KEY as the property name reference, which is not correct and over-complicated in two ways.

• We use a key format like COSMOS-KEY in KV because Key Vault doesn't support . in the secret name, but App Configuration can perfectly support that.
• When storing configurations in the App Configuration service, there's no need to list these properties in the bootstrap.properties or application.properties anymore.

Expected behavior
We should:

• Step 8 & 9 in convert to using App Configuration section, the key should be like /application/spring.cloud.azure.cosmos.* instead of /application/azure.cosmos.*
• Remove the three spring.cloud.azure.cosmos.* properties from the bootstrap.properties file.