Fix EventHandlerLoaderTest failing after PojoSerializerLoaderTest (#542)

Author: M-Elsaeed

aws-lambda-java-runtime-interface-client/src/test/java/com/amazonaws/services/lambda/runtime/api/client/PojoSerializerLoaderTest.java

@@ -7,6 +7,7 @@
 
 import com.amazonaws.services.lambda.runtime.CustomPojoSerializer;
 import com.amazonaws.services.lambda.runtime.serialization.PojoSerializer;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -31,6 +32,7 @@ class PojoSerializerLoaderTest {
     @Mock
     private CustomPojoSerializer mockSerializer;
 
+    @AfterEach
     @BeforeEach
     void setUp() throws Exception {
         resetStaticFields();