Patch deprecated mergeOptions usage

[whns]

Description

The following videojs.mergeOptions call used when adding or resetting overlay items:

videojs-overlay/src/plugin.js

Line 135 in f1fc449

const mergeOptions = videojs.mergeOptions(this.options, o);

results in this deprecation warning being triggered on VideoJS 8.x:
VIDEOJS: WARN: videojs.mergeOptions is deprecated and will be removed in 9.0; please use videojs.obj.merge instead.

(For additional context on the deprecation, see https://videojs.org/guides/videojs-7-to-8/#newly-deprecated-functions.)

Specific Changes proposed

This changeset patches the relevant callsite with the existing approach used within reset.

Existing approach:

videojs-overlay/src/plugin.js

Line 98 in f1fc449

const merge = videojs.obj && videojs.obj.merge || videojs.mergeOptions;

Patch: 914d2c9

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
• Reviewed by Two Core Contributors

[whns]

@wseymour15 Please let me know if there's any other details needed here or if this repo is no longer under active maintenance. Thanks!