Polish Exception Message

This error message provides more context around which credentials failed.

Issue gh-16494

core/src/main/java/org/springframework/security/authentication/ott/OneTimeTokenAuthenticationProvider.java

@@ -62,7 +62,7 @@ public Authentication authenticate(Authentication authentication) throws Authent
 			return authenticated;
 		}
 		catch (UsernameNotFoundException ex) {
-			throw new BadCredentialsException("Authentication failed.");
+			throw new BadCredentialsException("Failed to authenticate the one-time token");
 		}
 	}