userguide: fix spelling of security_result EVE field

This ensures that the correct spelling of the `security_result` EVE
field for RFB (as opposed to `security-result`) is also reflected in the
documentation.

Ticket: OISF#7210

doc/userguide/output/eve/eve-json-format.rst

@@ -1889,7 +1889,7 @@ Fields
 * "client_protocol_version.major", "client_protocol_version.minor": The RFB protocol version agreed by the client.
 * "authentication.security_type": Security type agreed upon in the logged transaction, e.g. ``2`` is VNC auth.
 * "authentication.vnc.challenge", "authentication.vnc.response": Only available when security type 2 is used. Contains the challenge and response byte buffers exchanged by the server and client as hex strings.
-* "authentication.security-result": Result of the authentication process (``OK``, ``FAIL`` or ``TOOMANY``).
+* "authentication.security_result": Result of the authentication process (``OK``, ``FAIL`` or ``TOOMANY``).
 * "screen_shared": Boolean value describing whether the client requested screen sharing.
 * "framebuffer": Contains metadata about the initial screen setup process. Only available when the handshake completed this far.
 * "framebuffer.width", "framebuffer.height": Screen size as offered by the server.
@@ -1919,7 +1919,7 @@ Example of RFB logging, with full VNC style authentication parameters:
         "challenge": "0805b790b58e967f2b350a0c99de3881",
         "response": "aecb26faeaaa62179636a5934bac1078"
       },
-      "security-result": "OK"
+      "security_result": "OK"
     },
     "screen_shared": false,
     "framebuffer": {