chore(alert): fix grammer issues suggested by coderabbit

apps/docs/content/docs/components/alert.mdx

@@ -55,10 +55,9 @@ Alerts are temporary notifications that provide concise feedback about an action
 
 ### isClosable
 
-If `isClosable` is true, a close button appears on the alert which closes it.
-It is set to false by default.
+If `isClosable` is true, a close button appears on the alert, which can be used to close it.
 
-> **Note**: If the `onClose` is passed, the close button is visible regardless of `isClosable` property.
+> **Note**: If the `onClose` is passed, the close button is visible regardless of the `isClosable` property.
 
 <CodeDemo title="isClosable" files={alertContent.isClosable} />