[BUG] Incorrect MySQL Flexible server version

### API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/mysql/resource-manager/Microsoft.DBforMySQL/FlexibleServers/stable/2023-12-30/FlexibleServers.json#L774

### API Spec version

2023-12-30

### Describe the bug

MySQL spec defines ServerVersion as enum with values 5.7 and 8.0.21, and this does not correspond to https://learn.microsoft.com/en-us/azure/mysql/concepts-version-policy#supported-mysql-versions (8.0.37 is the latest in 8, but thera are also 8.4.x and 9.1.x

### Expected behavior

It should allow to specify any supported version described in https://learn.microsoft.com/en-us/azure/mysql/concepts-version-policy#supported-mysql-versions

### Actual behavior

Fails

### Reproduction Steps

I am using via azurem terreform provider.

### Environment

_No response_

Start at the ServerVersion enum near line 774 of specification/mysql/resource-manager/Microsoft.DBforMySQL/FlexibleServers/stable/2023-12-30/FlexibleServers.json. Compare its values with the supported MySQL versions in the linked Azure version-policy documentation. Done means the API specification accepts the supported versions described there.

Written by the indexing model from the issue text.