fix(replay): Do not mangle _metadata in client options (#6600)

Exclude the `_metadata` field from being mangled which caused invalid replay envelope headers

Author: Lms24

rollup/plugins/bundlePlugins.js

@@ -109,6 +109,7 @@ export function makeTerserPlugin() {
           '_support',
           // TODO: Get rid of these once we use the SDK to send replay events
           '_prepareEvent', // replay uses client._prepareEvent
+          '_metadata', // replay uses client.getOptions()._metadata
         ],
       },
     },