Remove unused import

Issue gh-8589

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtTimestampValidator.java

@@ -15,20 +15,20 @@
  */
 package org.springframework.security.oauth2.jwt;
 
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+
 import org.springframework.security.oauth2.core.OAuth2Error;
 import org.springframework.security.oauth2.core.OAuth2ErrorCodes;
 import org.springframework.security.oauth2.core.OAuth2TokenValidator;
 import org.springframework.security.oauth2.core.OAuth2TokenValidatorResult;
 import org.springframework.util.Assert;
 
-import java.time.Clock;
-import java.time.Duration;
-import java.time.Instant;
-import java.time.format.DateTimeFormatter;
-import java.time.temporal.ChronoUnit;
-
 /**
  * An implementation of {@link OAuth2TokenValidator} for verifying claims in a Jwt-based access token
  *