Remove unnecessary "throws" declarations

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

java/google/registry/tools/AppEngineConnection.java

@@ -65,7 +65,7 @@ class AppEngineConnection implements Connection {
       memoize(() -> xsrfTokenManager.generateToken(getUserId()));
 
   @Override
-  public void prefetchXsrfToken() throws IOException {
+  public void prefetchXsrfToken() {
     // Cause XSRF token to be fetched, and then stay resident in cache (since it's memoized).
     xsrfToken.get();
   }