Make "throws" clause use IOException

Now that we've updated the oauth java6 package in the open source build, we
can safely replace "Exception" with "IOException" in the throws clause of the
method that calls AuthorizationCodeInstalledApp.authorize().

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=156057190

java/google/registry/tools/AuthModule.java

@@ -130,7 +130,7 @@ public class AuthModule {
     /** Initiate the login flow. */
     public static void login(
         GoogleAuthorizationCodeFlow flow,
-        @ClientScopeQualifier String clientScopeQualifier) throws Exception {
+        @ClientScopeQualifier String clientScopeQualifier) throws IOException {
       new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver())
           .authorize(clientScopeQualifier);
     }