Ignore Buffer() deprecation warning

This is caused by the ftp module, used in the pac-proxy-agent module,
because PAC URLs may be FTP. That proxy agent is in turn used inside
Mockttp for proxy support. This only appears in built packages
annoyingly, because it only fires for non-node_modules deprecations.

The issue itself isn't actually a security issue, it's here:
https://github.com/mscdex/node-ftp/blob/7dff82fc049a52f51803bdffb95ec1de383f9fac/lib/connection.js#L53

Author: pimterry

test/integration-test.spec.ts

@@ -78,6 +78,9 @@ describe('Integration test', function () {
                 if (d.toString().includes('ExperimentalWarning: The fs.promises API')) return;
                 // We use _stream_wrap, in some node versions this is deprecated, for now ignore it
                 if (d.toString().includes('The _stream_wrap module is deprecated')) return;
+                // Deprecation in 'ftp' module (from pac-proxy) - only appears in built package, not source,
+                // as node doesn't show these deprecations by default when fired within node_modules.
+                if (d.toString().includes('Buffer() is deprecated') && process.env.TEST_BUILT_TARBALL) return;
                 // If the config parent folder doesn't exist at all, we'll see an ENOENT, that's ok:
                 if (d.toString().includes('[ENOENT]')) return;