[DOCS] Fix extracted date (elastic#75918) (elastic#75976)

In the example, we have a date with year `2018` but the extracted date is `1998`.

Co-authored-by: David Pilato <[email protected]>

Author: jrodewig

docs/reference/ingest/processors/dissect.asciidoc

@@ -194,7 +194,7 @@ Reference key modifier example
 | *Pattern* | `[%{ts}] [%{level}] %{*p1}:%{&p1} %{*p2}:%{&p2}`
 | *Input*   | [2018-08-10T17:15:42,466] [ERR] ip:1.2.3.4 error:REFUSED
 | *Result*  a|
-* ts = 1998-08-10T17:15:42,466
+* ts = 2018-08-10T17:15:42,466
 * level = ERR
 * ip = 1.2.3.4
 * error = REFUSED