[BUG] fix disableWelcomeScreen config

disableWelcomeScreen was erroneously removed from being exposed to browser (for testing purposes)
and was not able to pass the config to disable the welcome screen showing.

Issue:
opensearch-project#1138

Signed-off-by: Kawika Avilla <kavilla414@gmail.com>

src/plugins/home/server/index.ts

@@ -39,7 +39,7 @@ import { configSchema, ConfigSchema } from '../config';
 
 export const config: PluginConfigDescriptor<ConfigSchema> = {
   exposeToBrowser: {
-    disableWelcomeScreen: false,
+    disableWelcomeScreen: true,
   },
   schema: configSchema,
   deprecations: ({ renameFromRoot }) => [