Remove legacy discover references and methods

[Tostti]

Description

From version 4.9.0, the legacy discover will not be available anymore.
There are currently references and methods related to that that need to be removed. This needs to be done once the latest changes for 4.8 are propagated.

Research

Here will be listed all the required changes that we find on the application:

• wazuh-dashboard-plugins/plugins/main/public/plugin.ts

  Line 63 in b988643

  localStorage.setItem('discover:deprecation-notice:show', 'false');

• wazuh-dashboard-plugins/plugins/main/public/controllers/overview/components/last-alerts-stat/last-alerts-stat.tsx

  Lines 65 to 66 in b988643

  	// Check if the new discover is enabled to build the URL
  	const v2Enabled = await core.uiSettings.get<boolean>('discover:v2');

• wazuh-dashboard-plugins/plugins/main/public/controllers/overview/components/last-alerts-stat/last-alerts-stat.tsx

  Lines 73 to 78 in b988643

  	if (!v2Enabled) {
  	discoverLocation = {
  	app: 'discoverLegacy',
  	basePath: '',
  	};
  	}