DRIVERS-3218 clarify label handling (#1892)

No behavior changes.

- Add the `RetryableError` error label to example code to match the description and implementations.
- Clarify non-backpressure errors should not add the backpressure label.

Author: kevinAlbs

source/connection-monitoring-and-pooling/connection-monitoring-and-pooling.md

@@ -291,10 +291,9 @@ Endpoint. The pool has the following properties:
     to avoid clearing the pool. The pool MUST NOT add the backpressure error labels during an authentication step
     after the `hello` message. For errors that the driver can distinguish as never occurring due to server overload,
     such as DNS lookup failures, non‑I/O TLS errors (e.g., certificate validation or hostname‑mismatch failures), or
-    errors encountered while establishing a connection to a SOCKS5 proxy, the driver MUST clear the connection pool and
-    MUST mark the server Unknown for these error types. In contrast, if an I/O error (for example, an EOF error) occurs
-    during the TLS handshake, the driver MUST treat it as a potential overload condition and MUST add the backpressure
-    error labels.
+    errors encountered while establishing a connection to a SOCKS5 proxy, the driver MUST NOT add backpressure error
+    labels for these error types. In contrast, if an I/O error (for example, an EOF error) occurs during the TLS
+    handshake, the driver MUST treat it as a potential overload condition and MUST add the backpressure error labels.
 
 ```typescript
 interface ConnectionPool {
@@ -472,7 +471,7 @@ try:
   return connection
 except error:
   close connection
-  add `SystemOverloadedError` label if appropriate (see "backpressure-enabled" in [Connection Pool](#connection-pool))
+  add `SystemOverloadedError` and `RetryableError` labels if appropriate (see "backpressure-enabled" in [Connection Pool](#connection-pool))
   throw error # Propagate error in manner idiomatic to language.
 ```