Modify mfaConfig default according to admin sdk integ tests

This is line is needed to avoid throwing an error on this line:
https://github.com/firebase/firebase-admin-node/blob/83fbb6d3ebc2088206a8eb5956326b2198a254e4/src/auth/auth-config.ts#L613

Author: lisajian

src/emulator/auth/operations.ts

@@ -2699,7 +2699,7 @@ function createTenant(
     enableEmailLinkSignin: reqBody.enableEmailLinkSignin ?? false,
     enableAnonymousUser: reqBody.enableAnonymousUser ?? false,
     disableAuth: reqBody.disableAuth ?? false,
-    mfaConfig: reqBody.mfaConfig ?? {},
+    mfaConfig: reqBody.mfaConfig ?? { state: "DISABLED" },
     tenantId: "", // Placeholder until one is generated
   };
 

src/test/emulators/auth/tenant.spec.ts

@@ -51,7 +51,9 @@ describeAuthEmulator("tenant management", ({ authApi }) => {
           expect(res.body.disableAuth).to.be.false;
           expect(res.body.enableAnonymousUser).to.be.false;
           expect(res.body.enableEmailLinkSignin).to.be.false;
-          expect(res.body.mfaConfig).to.eql({});
+          expect(res.body.mfaConfig).to.eql({
+            state: "DISABLED",
+          });
         });
     });
   });