Fix casing mistakes in env var doc (#4433)

Found some casing mistakes a few days back, taking the time now to do a pass on the env vars to fix them.

doc/EnvironmentVariables.md

@@ -57,7 +57,7 @@
 | Https_Proxy                             | Address of the proxy to use for outbound HTTPS requests                                                                                            | string                                                                |                               |
 | HttpSettings__Enabled                    | Whether the HTTP server should be enabled                                                                                                          | bool                                                                  | true                          |
 | HttpSettings__Port                       | The port for the HTTP protocol head to listen on                                                                                                   | int32                                                                 | 443                           |
-| HttpSettings__enableProxyPort           | Enable the HTTP protocol head to additionally listen on port 8080. This is only reachable by internally by Docker vNet and used by ApiProxy module | bool                                                                 | true                           |
+| HttpSettings__EnableProxyPort           | Enable the HTTP protocol head to additionally listen on port 8080. This is only reachable by internally by Docker vNet and used by ApiProxy module | bool                                                                 | true                           |
 | IotHubConnectionPoolSize                | Pool size for upstream AMQP connection                                                                                                             | int32                                                                 |                               |
 | MaxConnectedClients                     | Maximum number of downstream clients allowed to connect                                                                                            | int32                                                                 | 101 (100 clients + 1 EdgeHub) |
 | MaxUpstreamBatchSize                    | Max number of messages to concurrently send upstream                                                                                               | int32                                                                 | 10                            |