[BUG][Discover] Panel header says `Open search`

[kavilla]

Describe the bug
https://github.com/opensearch-project/OpenSearch-Dashboards/blob/main/src/plugins/discover/public/application/components/top_nav/open_search_panel.tsx#L70

To Reproduce
Navigate to Discover page, click on Open. Notice the header says Open search

Expected behavior
I believe it should say OpenSearch but even still I'm not quite that makes sense.

Dashboards Version
All

[bibaswan7]

Please assign it to me