fix contentful import for generate cmd

Author: bezoerb

lib/migration.js

@@ -6,7 +6,7 @@ const runMigration = require('contentful-migration/built/bin/cli').runMigration;
 const {
   getContentTypes,
   generateMigrationScript,
-} = require('contentful-cli/lib/cmds/space_cmds/generate_cmds/migration');
+} = require('contentful-cli/dist/lib/cmds/space_cmds/generate_cmds/migration');
 const pc = require('picocolors');
 const { getEnvironment } = require('./contentful');