fix: Fix deprecated API usage for Intellij Platform 2023.2

Author: ByteAurora

src/main/kotlin/com/github/ilovegamecoding/intellijcodexp/toolWindow/CodeXPToolWindowFactory.kt

@@ -53,7 +53,7 @@ class CodeXPToolWindowFactory : ToolWindowFactory {
         initializeUI()
 
         // Add the dashboard to the tool window
-        val contentFactory = ContentFactory.SERVICE.getInstance()
+        val contentFactory = ContentFactory.getInstance()
         val scrollPane = JBScrollPane(codeXPDashboardForm.pMain)
         val rootPanel = JPanel(BorderLayout())
         rootPanel.add(BorderLayout.CENTER, scrollPane)