Remove unnecessary "throws" declarations

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=201058582

javatests/google/registry/keyring/api/KeySerializerTest.java

@@ -139,7 +139,7 @@ public class KeySerializerTest {
     }
   }
 
-  @Test public void serializeString() throws Exception {
+  @Test public void serializeString() {
     String result = KeySerializer.deserializeString(KeySerializer.serializeString("value\n"));
     assertThat(result).isEqualTo("value\n");
   }