Add enum values to config properties docs

* Updated httpclient.pool.leasing-strategy, httpclient.pool.type and httpclient.proxy.type.

docs/modules/ROOT/partials/_configprops.adoc

@@ -84,18 +84,18 @@
 |spring.cloud.gateway.httpclient.max-initial-line-length |  | The max initial line length.
 |spring.cloud.gateway.httpclient.pool.acquire-timeout |  | Only for type FIXED, the maximum time in millis to wait for acquiring.
 |spring.cloud.gateway.httpclient.pool.eviction-interval | `+++0+++` | Perform regular eviction checks in the background at a specified interval. Disabled by default ({@link Duration#ZERO})
-|spring.cloud.gateway.httpclient.pool.leasing-strategy | `+++fifo+++` | Configures the leasing strategy for the pool, defaults to FIFO which is Netty's default.
+|spring.cloud.gateway.httpclient.pool.leasing-strategy | `+++fifo+++` | Configures the leasing strategy for the pool (fifo or lifo), defaults to FIFO which is Netty's default.
 |spring.cloud.gateway.httpclient.pool.max-connections |  | Only for type FIXED, the maximum number of connections before starting pending acquisition on existing ones.
 |spring.cloud.gateway.httpclient.pool.max-idle-time |  | Time in millis after which the channel will be closed. If NULL, there is no max idle time.
 |spring.cloud.gateway.httpclient.pool.max-life-time |  | Duration after which the channel will be closed. If NULL, there is no max life time.
 |spring.cloud.gateway.httpclient.pool.metrics | `+++false+++` | Enables channel pools metrics to be collected and registered in Micrometer. Disabled by default.
 |spring.cloud.gateway.httpclient.pool.name | `+++proxy+++` | The channel pool map name, defaults to proxy.
-|spring.cloud.gateway.httpclient.pool.type | `+++elastic+++` | Type of pool for HttpClient to use, defaults to ELASTIC.
+|spring.cloud.gateway.httpclient.pool.type | `+++elastic+++` | Type of pool for HttpClient to use (elastic, fixed or disabled).
 |spring.cloud.gateway.httpclient.proxy.host |  | Hostname for proxy configuration of Netty HttpClient.
 |spring.cloud.gateway.httpclient.proxy.non-proxy-hosts-pattern |  | Regular expression (Java) for a configured list of hosts. that should be reached directly, bypassing the proxy
 |spring.cloud.gateway.httpclient.proxy.password |  | Password for proxy configuration of Netty HttpClient.
 |spring.cloud.gateway.httpclient.proxy.port |  | Port for proxy configuration of Netty HttpClient.
-|spring.cloud.gateway.httpclient.proxy.type | `+++http+++` | proxyType for proxy configuration of Netty HttpClient.
+|spring.cloud.gateway.httpclient.proxy.type | `+++http+++` | proxyType for proxy configuration of Netty HttpClient (http, socks4 or socks5).
 |spring.cloud.gateway.httpclient.proxy.username |  | Username for proxy configuration of Netty HttpClient.
 |spring.cloud.gateway.httpclient.response-timeout |  | The response timeout.
 |spring.cloud.gateway.httpclient.ssl.close-notify-flush-timeout | `+++3000ms+++` | SSL close_notify flush timeout. Default to 3000 ms.