Fix identity pinning link. (#3395)

Author: pixlwave

ElementX/Sources/Application/AppSettings.swift

@@ -126,7 +126,7 @@ final class AppSettings {
     /// A URL where users can go read more about the chat backup.
     let chatBackupDetailsURL: URL = "https://element.io/help#encryption5"
     /// A URL where users can go read more about identity pinning violations
-    let identityPinningViolationDetailsURL: URL = "https://element.io/help#18"
+    let identityPinningViolationDetailsURL: URL = "https://element.io/help#encryption18"
     /// Any domains that Element web may be hosted on - used for handling links.
     let elementWebHosts = ["app.element.io", "staging.element.io", "develop.element.io"]