Update AtUri import to use official package with fix for usernames that start with numbers (close #414) (#418)

src/view/com/post-thread/PostThreadItem.tsx

@@ -2,7 +2,7 @@ import React from 'react'
 import {observer} from 'mobx-react-lite'
 import {Linking, StyleSheet, View} from 'react-native'
 import Clipboard from '@react-native-clipboard/clipboard'
-import {AtUri} from '../../../third-party/uri'
+import {AtUri} from '@atproto/api'
 import {
   FontAwesomeIcon,
   FontAwesomeIconStyle,