chore: remove unnecessary if condition

source: openfga/sdk-generator#546

Author: AlessandroMinoccheri

src/main/java/dev/openfga/sdk/api/model/AbstractOpenApiSchema.java

@@ -137,8 +137,7 @@ public int hashCode() {
     public Boolean isNullable() {
         if (Boolean.TRUE.equals(isNullable)) {
             return Boolean.TRUE;
-        } else {
-            return Boolean.FALSE;
         }
+        return Boolean.FALSE;
     }
 }